HTML Standard

2024.09.04 00:39

HTML Standard

HTML

Living Standard — Last Updated 29 August 2024 ← 4.10.5 The input element — Table of Contents — 4.10.17 Form control infrastructure → 4.10.6 The button element 4.10.7 The select element 4.10.8 The datalist element 4.10.9 The optgroup element 4.10.10 The option element 4.10.11 The textarea element 4.10.12 The output element 4.10.13 The progress element 4.10.14 The meter element 4.10.15 The fieldset element 4.10.16 The legend element

4.10.6 The button element

✔ MDN

Element/button

Support in all current engines. Firefox 1+ Safari 4+ Chrome 1+ Opera 15+ Edge 79+ Edge (Legacy) 12+ Internet Explorer Yes Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 14+ ✔ MDN

HTMLButtonElement

Support in all current engines. Firefox 1+ Safari 3+ Chrome 1+ Opera 12.1+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 5.5+ Firefox Android ? Safari iOS 1+ Chrome Android ? WebView Android 37+ Samsung Internet ? Opera Android 12.1+ Categories : Flow content . Phrasing content . Interactive content . Listed , labelable , submittable , and autocapitalize-and-autocorrect inheriting form-associated element . Palpable content . Contexts in which this element can be used : Where phrasing content is expected. Content model : Phrasing content , but there must be no interactive content descendant and no descendant with the tabindex attribute specified. Tag omission in text/html : Neither tag is omissible. Content attributes : Global attributes disabled — Whether the form control is disabled form — Associates the element with a form element formaction — URL to use for form submission formenctype — Entry list encoding type to use for form submission formmethod — Variant to use for form submission formnovalidate — Bypass form control validation for form submission formtarget — Navigable for form submission name — Name of the element to use for form submission and in the form.elements API popovertarget — Targets a popover element to toggle, show, or hide popovertargetaction — Indicates whether a targeted popover element is to be toggled, shown, or hidden type — Type of button value — Value to be used for form submission Accessibility considerations : For authors . For implementers . DOM interface : [ Exposed = Window ] interface HTMLButtonElement : HTMLElement { [ HTMLConstructor ] constructor (); [ CEReactions ] attribute boolean disabled ; readonly attribute HTMLFormElement ? form ; [ CEReactions ] attribute USVString formAction ; [ CEReactions ] attribute DOMString formEnctype ; [ CEReactions ] attribute DOMString formMethod ; [ CEReactions ] attribute boolean formNoValidate ; [ CEReactions ] attribute DOMString formTarget ; [ CEReactions ] attribute DOMString name ; [ CEReactions ] attribute DOMString type ; [ CEReactions ] attribute DOMString value ; readonly attribute boolean willValidate ; readonly attribute ValidityState validity ; readonly attribute DOMString validationMessage ; boolean checkValidity (); boolean reportValidity (); undefined setCustomValidity ( DOMString error ); readonly attribute NodeList labels ; }; HTMLButtonElement includes PopoverInvokerElement ;

The button element represents a button labeled by its contents.

The element is a button .

The type attribute controls the behavior of the button when it is activated. It is an enumerated attribute with the following keywords and states:

Keyword State Brief description submit Submit Button Submits the form. reset Reset Button Resets the form. button Button Does nothing.

The attribute's missing value default and invalid value default are both the Submit Button state.

If the type attribute is in the Submit Button state, the element is specifically a submit button .

Constraint validation : If the type attribute is in the Reset Button state or the Button state, the element is barred from constraint validation .

A button element element 's activation behavior given event is:

If element is disabled , then return.

If element 's node document is not fully active , then return.

If element has a form owner then switch on element 's type attribute's state, then:

Submit Button

Submit element 's form owner from element with userInvolvement set to event 's user navigation involvement . Reset Button

Reset element 's form owner . Button

Do nothing.

Run the popover target attribute activation behavior given element .

The form attribute is used to explicitly associate the button element with its form owner . The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The formaction , formenctype , formmethod , formnovalidate , and formtarget attributes are attributes for form submission .

The formnovalidate attribute can be used to make submit buttons that do not trigger the constraint validation.

The formaction , formenctype , formmethod , formnovalidate , and formtarget must not be specified if the element's type attribute is not in the Submit Button state.

The value attribute gives the element's value for the purposes of form submission. The element's value is the value of the element's value attribute, if there is one, or the empty string otherwise.

A button (and its value) is only included in the form submission if the button itself was used to initiate the form submission.

The value IDL attribute must reflect the content attribute of the same name.

The type IDL attribute must reflect the content attribute of the same name, limited to only known values .

The following button is labeled "Show hint" and pops up a dialog box when activated:

button type = button onclick = alert('This 15-20 minute piece was composed by George Gershwin.') Show hint / button

4.10.7 The select element

✔ MDN

Element/select

Support in all current engines. Firefox 1+ Safari 1+ Chrome 1+ Opera 2+ Edge 79+ Edge (Legacy) 12+ Internet Explorer Yes Firefox Android 4+ Safari iOS ? Chrome Android ? WebView Android 37+ Samsung Internet ? Opera Android 10.1+ ✔ MDN

HTMLSelectElement

Support in all current engines. Firefox 1+ Safari 1+ Chrome 1+ Opera 2+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 1+ Firefox Android 4+ Safari iOS ? Chrome Android ? WebView Android 37+ Samsung Internet ? Opera Android 10.1+ Categories : Flow content . Phrasing content . Interactive content . Listed , labelable , submittable , resettable , and autocapitalize-and-autocorrect inheriting form-associated element . Palpable content . Contexts in which this element can be used : Where phrasing content is expected. Content model : Zero or more option , optgroup , hr , and script-supporting elements. Tag omission in text/html : Neither tag is omissible. Content attributes : Global attributes autocomplete — Hint for form autofill feature disabled — Whether the form control is disabled form — Associates the element with a form element multiple — Whether to allow multiple values name — Name of the element to use for form submission and in the form.elements API required — Whether the control is required for form submission size — Size of the control Accessibility considerations : If the element has a multiple attribute or a size attribute with a value > 1: for authors ; for implementers . Otherwise: for authors ; for implementers . DOM interface : [ Exposed = Window ] interface HTMLSelectElement : HTMLElement { [ HTMLConstructor ] constructor (); [ CEReactions ] attribute DOMString autocomplete ; [ CEReactions ] attribute boolean disabled ; readonly attribute HTMLFormElement ? form ; [ CEReactions ] attribute boolean multiple ; [ CEReactions ] attribute DOMString name ; [ CEReactions ] attribute boolean required ; [ CEReactions ] attribute unsigned long size ; readonly attribute DOMString type ; [ SameObject ] readonly attribute HTMLOptionsCollection options ; [ CEReactions ] attribute unsigned long length ; getter HTMLOptionElement ? item ( unsigned long index ); HTMLOptionElement ? namedItem ( DOMString name ); [ CEReactions ] undefined add (( HTMLOptionElement or HTMLOptGroupElement ) element , optional ( HTMLElement or long )? before = null ); [ CEReactions ] undefined remove (); // ChildNode overload [ CEReactions ] undefined remove ( long index ); [ CEReactions ] setter undefined ( unsigned long index , HTMLOptionElement ? option ); [ SameObject ] readonly attribute HTMLCollection selectedOptions ; attribute long selectedIndex ; attribute DOMString value ; readonly attribute boolean willValidate ; readonly attribute ValidityState validity ; readonly attribute DOMString validationMessage ; boolean checkValidity (); boolean reportValidity (); undefined setCustomValidity ( DOMString error ); undefined showPicker (); readonly attribute NodeList labels ; };

The select element represents a control for selecting amongst a set of options.

✔ MDN

Attributes/multiple

Support in all current engines. Firefox 1+ Safari 3+ Chrome 1+ Opera ? Edge 79+ Edge (Legacy) 12+ Internet Explorer Yes Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android ?

The multiple attribute is a boolean attribute . If the attribute is present, then the select element represents a control for selecting zero or more options from the list of options . If the attribute is absent, then the select element represents a control for selecting a single option from the list of options .

✔ MDN

Attributes/size

The size attribute gives the number of options to show to the user. The size attribute, if specified, must have a value that is a valid non-negative integer greater than zero.

The display size of a select element is the result of applying the rules for parsing non-negative integers to the value of element's size attribute, if it has one and parsing it is successful. If applying those rules to the attribute's value is not successful, or if the size attribute is absent, then the element's display size is 4 if the element's multiple content attribute is present, and 1 otherwise.

The list of options for a select element consists of all the option element children of the select element, and all the option element children of all the optgroup element children of the select element, in tree order .

✔ MDN

Attributes/required

Support in all current engines. Firefox 4+ Safari 5.1+ Chrome 10+ Opera ? Edge 79+ Edge (Legacy) 12+ Internet Explorer 10+ Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android ?

The required attribute is a boolean attribute . When specified, the user will be required to select a value before submitting the form.

If a select element has a required attribute specified, does not have a multiple attribute specified, and has a display size of 1; and if the value of the first option element in the select element's list of options (if any) is the empty string, and that option element's parent node is the select element (and not an optgroup element), then that option is the select element's placeholder label option .

If a select element has a required attribute specified, does not have a multiple attribute specified, and has a display size of 1, then the select element must have a placeholder label option .

In practice, the requirement stated in the paragraph above can only apply when a select element does not have a size attribute with a value greater than 1.

Constraint validation : If the element has its required attribute specified, and either none of the option elements in the select element's list of options have their selectedness set to true, or the only option element in the select element's list of options with its selectedness set to true is the placeholder label option , then the element is suffering from being missing .

If the multiple attribute is absent, and the element is not disabled , then the user agent should allow the user to pick an option element in its list of options that is itself not disabled . Upon this option element being picked (either through a click, or through unfocusing the element after changing its value, or through a menu command , or through any other mechanism), and before the relevant user interaction event is queued (e.g. before the click event), the user agent must set the selectedness of the picked option element to true, set its dirtiness to true, and then send select update notifications .

If the multiple attribute is absent, whenever an option element in the select element's list of options has its selectedness set to true, and whenever an option element with its selectedness set to true is added to the select element's list of options , the user agent must set the selectedness of all the other option elements in its list of options to false.

If the multiple attribute is absent and the element's display size is greater than 1, then the user agent should also allow the user to request that the option whose selectedness is true, if any, be unselected. Upon this request being conveyed to the user agent, and before the relevant user interaction event is queued (e.g. before the click event), the user agent must set the selectedness of that option element to false, set its dirtiness to true, and then send select update notifications .

The selectedness setting algorithm , given a select element element , is to run the following steps:

If element 's multiple attribute is absent, and element 's display size is 1, and no option elements in the element 's list of options have their selectedness set to true, then set the selectedness of the first option element in the list of options in tree order that is not disabled , if any, to true, and return.

If element 's multiple attribute is absent, and two or more option elements in element 's list of options have their selectedness set to true, then set the selectedness of all but the last option element with its selectedness set to true in the list of options in tree order to false.

The option HTML element insertion steps , given insertedNode , are:

If insertedNode 's parent is a select element, or insertedNode 's parent is an optgroup element whose parent is a select element, then run that select element's selectedness setting algorithm .

The option HTML element removing steps , given removedNode and oldParent , are:

If oldParent is a select element, or oldParent is an optgroup element whose parent is a select element, then run that select element's selectedness setting algorithm .

The optgroup HTML element removing steps , given removedNode and oldParent , are:

If oldParent is a select element and removedNode has an option child, then run oldParent 's selectedness setting algorithm .

If an option element in the list of options asks for a reset , then run that select element's selectedness setting algorithm .

If the multiple attribute is present, and the element is not disabled , then the user agent should allow the user to toggle the selectedness of the option elements in its list of options that are themselves not disabled . Upon such an element being toggled (either through a click, or through a menu command , or any other mechanism), and before the relevant user interaction event is queued (e.g. before a related click event), the selectedness of the option element must be changed (from true to false or false to true), the dirtiness of the element must be set to true, and the user agent must send select update notifications .

When the user agent is to send select update notifications , queue an element task on the user interaction task source given the select element to run these steps:

Set the select element's user validity to true.

Fire an event named input at the select element, with the bubbles and composed attributes initialized to true.

Fire an event named change at the select element, with the bubbles attribute initialized to true.

The reset algorithm for a select element selectElement is:

Set selectElement 's user validity to false.

For each optionElement of selectElement 's list of options :

If optionElement has a selected attribute, then set optionElement 's selectedness to true; otherwise set it to false.

Set optionElement 's dirtiness to false.

Run the selectedness setting algorithm given selectElement .

The form attribute is used to explicitly associate the select element with its form owner . The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autocomplete attribute controls how the user agent provides autofill behavior.

A select element that is not disabled is mutable .

select . type ✔ MDN

HTMLSelectElement/type

Support in all current engines. Firefox 1+ Safari 3+ Chrome 1+ Opera 2+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 1+ Firefox Android ? Safari iOS 1+ Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 10.1+

Returns " select-multiple " if the element has a multiple attribute, and " select-one " otherwise.

select . options ✔ MDN

HTMLSelectElement/options

Returns an HTMLOptionsCollection of the list of options . select . length [ = value ]

Returns the number of elements in the list of options .

When set to a smaller number, truncates the number of option elements in the select .

When set to a greater number, adds new blank option elements to the select .

element = select . item ( index ) ✔ MDN

HTMLSelectElement/item

Returns the item with index index from the list of options . The items are sorted in tree order .

element = select . namedItem ( name ) ✔ MDN

HTMLSelectElement/namedItem

Support in all current engines. Firefox 1+ Safari 3+ Chrome 1+ Opera 12.1+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 6+ Firefox Android ? Safari iOS 1+ Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 12.1+

Returns the first item with ID or name name from the list of options .

Returns null if no element with that ID could be found.

select . add ( element [, before ]) ✔ MDN

HTMLSelectElement/add

Inserts element before the node given by before .

The before argument can be a number, in which case element is inserted before the item with that number, or an element from the list of options , in which case element is inserted before that element.

If before is omitted, null, or a number out of range, then element will be added at the end of the list.

This method will throw a " HierarchyRequestError " DOMException if element is an ancestor of the element into which it is to be inserted.

select . selectedOptions ✔ MDN

HTMLSelectElement/selectedOptions

Support in all current engines. Firefox 26+ Safari 6+ Chrome 19+ Opera 9+ Edge 79+ Edge (Legacy) 12+ Internet Explorer No Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 10.1+

Returns an HTMLCollection of the list of options that are selected.

select . selectedIndex [ = value ] ✔ MDN

HTMLSelectElement/selectedIndex

Returns the index of the first selected item, if any, or −1 if there is no selected item.

Can be set, to change the selection.

select . value [ = value ]

Returns the value of the first selected item, if any, or the empty string if there is no selected item.

Can be set, to change the selection.

select . showPicker ()

Shows any applicable picker UI for select , so that the user can select a value.

Throws an " InvalidStateError " DOMException if select is not mutable .

Throws a " NotAllowedError " DOMException if called without transient user activation .

Throws a " SecurityError " DOMException if select is inside a cross-origin iframe .

Throws a " NotSupportedError " DOMException if select is not being rendered .

The type IDL attribute, on getting, must return the string " select-one " if the multiple attribute is absent, and the string " select-multiple " if the multiple attribute is present.

The options IDL attribute must return an HTMLOptionsCollection rooted at the select node, whose filter matches the elements in the list of options .

The options collection is also mirrored on the HTMLSelectElement object. The supported property indices at any instant are the indices supported by the object returned by the options attribute at that instant.

The length IDL attribute must return the number of nodes represented by the options collection. On setting, it must act like the attribute of the same name on the options collection.

The item( index ) method must return the value returned by the method of the same name on the options collection, when invoked with the same argument.

The namedItem( name ) method must return the value returned by the method of the same name on the options collection, when invoked with the same argument.

When the user agent is to set the value of a new indexed property or set the value of an existing indexed property for a select element, it must instead run the corresponding algorithm on the select element's options collection.

Similarly, the add( element , before ) method must act like its namesake method on that same options collection.

✔ MDN

HTMLSelectElement/remove

The remove() method must act like its namesake method on that same options collection when it has arguments, and like its namesake method on the ChildNode interface implemented by the HTMLSelectElement ancestor interface Element when it has no arguments.

The selectedOptions IDL attribute must return an HTMLCollection rooted at the select node, whose filter matches the elements in the list of options that have their selectedness set to true.

The selectedIndex IDL attribute, on getting, must return the index of the first option element in the list of options in tree order that has its selectedness set to true, if any. If there isn't one, then it must return −1.

On setting, the selectedIndex attribute must set the selectedness of all the option elements in the list of options to false, and then the option element in the list of options whose index is the given new value, if any, must have its selectedness set to true and its dirtiness set to true.

This can result in no element having a selectedness set to true even in the case of the select element having no multiple attribute and a display size of 1.

The value IDL attribute, on getting, must return the value of the first option element in the list of options in tree order that has its selectedness set to true, if any. If there isn't one, then it must return the empty string.

On setting, the value attribute must set the selectedness of all the option elements in the list of options to false, and then the first option element in the list of options , in tree order , whose value is equal to the given new value, if any, must have its selectedness set to true and its dirtiness set to true.

This can result in no element having a selectedness set to true even in the case of the select element having no multiple attribute and a display size of 1.

The multiple , required , and size IDL attributes must reflect the respective content attributes of the same name. The size IDL attribute has a default value of 0.

For historical reasons, the default value of the size IDL attribute does not return the actual size used, which, in the absence of the size content attribute, is either 1 or 4 depending on the presence of the multiple attribute.

The following example shows how a select element can be used to offer the user with a set of options from which the user can select a single option. The default option is preselected.

p label for = unittype Select unit type: / label select id = unittype name = unittype option value = 1 Miner / option option value = 2 Puffer / option option value = 3 selected Snipey / option option value = 4 Max / option option value = 5 Firebot / option / select / p

When there is no default option, a placeholder can be used instead:

select name = unittype required option value = Select unit type / option option value = 1 Miner / option option value = 2 Puffer / option option value = 3 Snipey / option option value = 4 Max / option option value = 5 Firebot / option / select

Here, the user is offered a set of options from which they can select any number. By default, all five options are selected.

p label for = allowedunits Select unit types to enable on this map: / label select id = allowedunits name = allowedunits multiple option value = 1 selected Miner / option option value = 2 selected Puffer / option option value = 3 selected Snipey / option option value = 4 selected Max / option option value = 5 selected Firebot / option / select / p

Sometimes, a user has to select one or more items. This example shows such an interface.

label Select the songs from that you would like on your Act II Mix Tape: select multiple required name = act2 option value = s1 It Sucks to Be Me (Reprise) option value = s2 There is Life Outside Your Apartment option value = s3 The More You Ruv Someone option value = s4 Schadenfreude option value = s5 I Wish I Could Go Back to College option value = s6 The Money Song option value = s7 School for Monsters option value = s8 The Money Song (Reprise) option value = s9 There's a Fine, Fine Line (Reprise) option value = s10 What Do You Do With a B.A. in English? (Reprise) option value = s11 For Now / select / label

Occasionally it can be useful to have a separator: label Select the song to play next: select required name = next option value = sr Random hr option value = s1 It Sucks to Be Me (Reprise) option value = s2 There is Life Outside Your Apartment …

4.10.8 The datalist element

MDN

Element/datalist Firefox 🔰 4+ Safari 12.1+ Chrome 20+ Opera 9.5+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 10+ Firefox Android 🔰 79+ Safari iOS ? Chrome Android 33+ WebView Android ? Samsung Internet ? Opera Android ? ✔ MDN

HTMLDataListElement

Support in all current engines. Firefox 4+ Safari 12.1+ Chrome 20+ Opera 12.1+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 10+ Firefox Android ? Safari iOS ? Chrome Android ? WebView Android 4.4.3+ Samsung Internet ? Opera Android 12.1+ Categories : Flow content . Phrasing content . Contexts in which this element can be used : Where phrasing content is expected. Content model : Either: phrasing content . Or: Zero or more option and script-supporting elements. Tag omission in text/html : Neither tag is omissible. Content attributes : Global attributes Accessibility considerations : For authors . For implementers . DOM interface : [ Exposed = Window ] interface HTMLDataListElement : HTMLElement { [ HTMLConstructor ] constructor (); [ SameObject ] readonly attribute HTMLCollection options ; };

The datalist element represents a set of option elements that represent predefined options for other controls. In the rendering, the datalist element represents nothing and it, along with its children, should be hidden.

The datalist element can be used in two ways. In the simplest case, the datalist element has just option element children.

label Animal: input name = animal list = animals datalist id = animals option value = Cat option value = Dog / datalist / label

In the more elaborate case, the datalist element can be given contents that are to be displayed for down-level clients that don't support datalist . In this case, the option elements are provided inside a select element inside the datalist element.

label Animal: input name = animal list = animals / label datalist id = animals label or select from the list: select name = animal option value = option Cat option Dog / select / label / datalist

The datalist element is hooked up to an input element using the list attribute on the input element.

Each option element that is a descendant of the datalist element, that is not disabled , and whose value is a string that isn't the empty string, represents a suggestion. Each suggestion has a value and a label . datalist . options

Returns an HTMLCollection of the option elements of the datalist element.

The options IDL attribute must return an HTMLCollection rooted at the datalist node, whose filter matches option elements.

Constraint validation : If an element has a datalist element ancestor, it is barred from constraint validation .

4.10.9 The optgroup element

✔ MDN

Element/optgroup

Support in all current engines. Firefox 1+ Safari 4+ Chrome 1+ Opera ? Edge 79+ Edge (Legacy) 12+ Internet Explorer 5.5+ Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android ? ✔ MDN

HTMLOptGroupElement

Support in all current engines. Firefox 1+ Safari 3+ Chrome 1+ Opera 12.1+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 5.5+ Firefox Android ? Safari iOS 1+ Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 12.1+ Categories : None. Contexts in which this element can be used : As a child of a select element. Content model : Zero or more option and script-supporting elements. Tag omission in text/html : An optgroup element's end tag can be omitted if the optgroup element is immediately followed by another optgroup element, if it is immediately followed by an hr element, or if there is no more content in the parent element. Content attributes : Global attributes disabled — Whether the form control is disabled label — User-visible label Accessibility considerations : For authors . For implementers . DOM interface : [ Exposed = Window ] interface HTMLOptGroupElement : HTMLElement { [ HTMLConstructor ] constructor (); [ CEReactions ] attribute boolean disabled ; [ CEReactions ] attribute DOMString label ; };

The optgroup element represents a group of option elements with a common label.

The element's group of option elements consists of the option elements that are children of the optgroup element.

When showing option elements in select elements, user agents should show the option elements of such groups as being related to each other and separate from other option elements.

✔ MDN

Attributes/disabled

Support in all current engines. Firefox 1+ Safari 4+ Chrome 1+ Opera ? Edge 79+ Edge (Legacy) 12+ Internet Explorer 8+ Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android ?

The disabled attribute is a boolean attribute and can be used to disable a group of option elements together.

The label attribute must be specified. Its value gives the name of the group, for the purposes of the user interface. User agents should use this attribute's value when labeling the group of option elements in a select element.

The disabled and label attributes must reflect the respective content attributes of the same name.

There is no way to select an optgroup element. Only option elements can be selected. An optgroup element merely provides a label for a group of option elements.

The following snippet shows how a set of lessons from three courses could be offered in a select drop-down widget:

form action = courseselector.dll method = get p Which course would you like to watch today? p label Course: select name = c optgroup label = 8.01 Physics I: Classical Mechanics option value = 8.01.1 Lecture 01: Powers of Ten option value = 8.01.2 Lecture 02: 1D Kinematics option value = 8.01.3 Lecture 03: Vectors optgroup label = 8.02 Electricity and Magnetism option value = 8.02.1 Lecture 01: What holds our world together? option value = 8.02.2 Lecture 02: Electric Field option value = 8.02.3 Lecture 03: Electric Flux optgroup label = 8.03 Physics III: Vibrations and Waves option value = 8.03.1 Lecture 01: Periodic Phenomenon option value = 8.03.2 Lecture 02: Beats option value = 8.03.3 Lecture 03: Forced Oscillations with Damping / select / label p input type = submit value = ▶ Play / form

4.10.10 The option element

✔ MDN

Element/option

Support in all current engines. Firefox 1+ Safari 4+ Chrome 1+ Opera ? Edge 79+ Edge (Legacy) 12+ Internet Explorer Yes Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android ? ✔ MDN

HTMLOptionElement

Support in all current engines. Firefox 1+ Safari 1.2+ Chrome 1+ Opera 12.1+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 5.5+ Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 12.1+ Categories : None. Contexts in which this element can be used : As a child of a select element. As a child of a datalist element. As a child of an optgroup element. Content model : If the element has a label attribute and a value attribute: Nothing . If the element has a label attribute but no value attribute: Text . If the element has no label attribute and is not a child of a datalist element: Text that is not inter-element whitespace . If the element has no label attribute and is a child of a datalist element: Text . Tag omission in text/html : An option element's end tag can be omitted if the option element is immediately followed by another option element, if it is immediately followed by an optgroup element, if it is immediately followed by an hr element, or if there is no more content in the parent element. Content attributes : Global attributes disabled — Whether the form control is disabled label — User-visible label selected — Whether the option is selected by default value — Value to be used for form submission Accessibility considerations : For authors . For implementers . DOM interface : [ Exposed = Window , LegacyFactoryFunction = Option ( optional DOMString text = , optional DOMString value , optional boolean defaultSelected = false , optional boolean selected = false )] interface HTMLOptionElement : HTMLElement { [ HTMLConstructor ] constructor (); [ CEReactions ] attribute boolean disabled ; readonly attribute HTMLFormElement ? form ; [ CEReactions ] attribute DOMString label ; [ CEReactions ] attribute boolean defaultSelected ; attribute boolean selected ; [ CEReactions ] attribute DOMString value ; [ CEReactions ] attribute DOMString text ; readonly attribute long index ; };

The option element represents an option in a select element or as part of a list of suggestions in a datalist element.

In certain circumstances described in the definition of the select element, an option element can be a select element's placeholder label option . A placeholder label option does not represent an actual option, but instead represents a label for the select control.

✔ MDN

Attributes/disabled

The disabled attribute is a boolean attribute . An option element is disabled if its disabled attribute is present or if it is a child of an optgroup element whose disabled attribute is present.

An option element that is disabled must prevent any click events that are queued on the user interaction task source from being dispatched on the element.

The label attribute provides a label for element. The label of an option element is the value of the label content attribute, if there is one and its value is not the empty string, or, otherwise, the value of the element's text IDL attribute.

The label content attribute, if specified, must not be empty.

The value attribute provides a value for element. The value of an option element is the value of the value content attribute, if there is one, or, if there is not, the value of the element's text IDL attribute.

The selected attribute is a boolean attribute . It represents the default selectedness of the element.

The dirtiness of an option element is a boolean state, initially false. It controls whether adding or removing the selected content attribute has any effect.

The selectedness of an option element is a boolean state, initially false. Except where otherwise specified, when the element is created, its selectedness must be set to true if the element has a selected attribute. Whenever an option element's selected attribute is added, if its dirtiness is false, its selectedness must be set to true. Whenever an option element's selected attribute is removed , if its dirtiness is false, its selectedness must be set to false.

The Option() constructor, when called with three or fewer arguments, overrides the initial state of the selectedness state to always be false even if the third argument is true (implying that a selected attribute is to be set). The fourth argument can be used to explicitly set the initial selectedness state when using the constructor.

A select element whose multiple attribute is not specified must not have more than one descendant option element with its selected attribute set.

An option element's index is the number of option elements that are in the same list of options but that come before it in tree order . If the option element is not in a list of options , then the option element's index is zero.

option . selected

Returns true if the element is selected, and false otherwise.

Can be set, to override the current state of the element.

option . index

Returns the index of the element in its select element's options list. option . form

Returns the element's form element, if any, or null otherwise. option . text

Same as textContent , except that spaces are collapsed and script elements are skipped.

option = new Option ([ text [, value [, defaultSelected [, selected ] ] ] ]) ✔ MDN

HTMLOptionElement/Option

Returns a new option element.

The text argument sets the contents of the element.

The value argument sets the value attribute.

The defaultSelected argument sets the selected attribute.

The selected argument sets whether or not the element is selected. If it is omitted, even if the defaultSelected argument is true, the element is not selected.

The disabled IDL attribute must reflect the content attribute of the same name. The defaultSelected IDL attribute must reflect the selected content attribute.

The label IDL attribute, on getting, if there is a label content attribute, must return that attribute's value; otherwise, it must return the element's label . On setting, the element's label content attribute must be set to the new value.

The value IDL attribute, on getting, must return the element's value . On setting, the element's value content attribute must be set to the new value.

The selected IDL attribute, on getting, must return true if the element's selectedness is true, and false otherwise. On setting, it must set the element's selectedness to the new value, set its dirtiness to true, and then cause the element to ask for a reset .

The index IDL attribute must return the element's index .

The text IDL attribute, on getting, must return the result of stripping and collapsing ASCII whitespace from the concatenation of data of all the Text node descendants of the option element, in tree order , excluding any that are descendants of descendants of the option element that are themselves script or SVG script elements.

The text attribute's setter must string replace all with the given value within this element.

The form IDL attribute's behavior depends on whether the option element is in a select element or not. If the option has a select element as its parent, or has an optgroup element as its parent and that optgroup element has a select element as its parent, then the form IDL attribute must return the same value as the form IDL attribute on that select element. Otherwise, it must return null.

A legacy factory function is provided for creating HTMLOptionElement objects (in addition to the factory methods from DOM such as createElement() ): Option( text , value , defaultSelected , selected ) . When invoked, the legacy factory function must perform the following steps:

Let document be the current global object 's associated Document .

Let option be the result of creating an element given document , option , and the HTML namespace .

If text is not the empty string, then append to option a new Text node whose data is text .

If value is given, then set an attribute value for option using " value " and value .

If defaultSelected is true, then set an attribute value for option using " selected " and the empty string.

If selected is true, then set option 's selectedness to true; otherwise set its selectedness to false (even if defaultSelected is true).

Return option .

4.10.11 The textarea element

✔ MDN

Element/textarea

Support in all current engines. Firefox 1+ Safari 4+ Chrome 1+ Opera 12.1+ Edge 79+ Edge (Legacy) 12+ Internet Explorer Yes Firefox Android ? Safari iOS 3+ Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 12.1+ ✔ MDN

HTMLTextAreaElement

Support in all current engines. Firefox 1+ Safari 1+ Chrome 1+ Opera 8+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 5+ Firefox Android ? Safari iOS ? Chrome Android ? WebView Android 37+ Samsung Internet ? Opera Android 10.1+ Categories : Flow content . Phrasing content . Interactive content . Listed , labelable , submittable , resettable , and autocapitalize-and-autocorrect inheriting form-associated element . Palpable content . Contexts in which this element can be used : Where phrasing content is expected. Content model : Text . Tag omission in text/html : Neither tag is omissible. Content attributes : Global attributes autocomplete — Hint for form autofill feature cols — Maximum number of characters per line dirname — Name of form control to use for sending the element's directionality in form submission disabled — Whether the form control is disabled form — Associates the element with a form element maxlength — Maximum length of value minlength — Minimum length of value name — Name of the element to use for form submission and in the form.elements API placeholder — User-visible label to be placed within the form control readonly — Whether to allow the value to be edited by the user required — Whether the control is required for form submission rows — Number of lines to show wrap — How the value of the form control is to be wrapped for form submission Accessibility considerations : For authors . For implementers . DOM interface : [ Exposed = Window ] interface HTMLTextAreaElement : HTMLElement { [ HTMLConstructor ] constructor (); [ CEReactions ] attribute DOMString autocomplete ; [ CEReactions ] attribute unsigned long cols ; [ CEReactions ] attribute DOMString dirName ; [ CEReactions ] attribute boolean disabled ; readonly attribute HTMLFormElement ? form ; [ CEReactions ] attribute long maxLength ; [ CEReactions ] attribute long minLength ; [ CEReactions ] attribute DOMString name ; [ CEReactions ] attribute DOMString placeholder ; [ CEReactions ] attribute boolean readOnly ; [ CEReactions ] attribute boolean required ; [ CEReactions ] attribute unsigned long rows ; [ CEReactions ] attribute DOMString wrap ; readonly attribute DOMString type ; [ CEReactions ] attribute DOMString defaultValue ; attribute [ LegacyNullToEmptyString ] DOMString value ; readonly attribute unsigned long textLength ; readonly attribute boolean willValidate ; readonly attribute ValidityState validity ; readonly attribute DOMString validationMessage ; boolean checkValidity (); boolean reportValidity (); undefined setCustomValidity ( DOMString error ); readonly attribute NodeList labels ; undefined select (); attribute unsigned long selectionStart ; attribute unsigned long selectionEnd ; attribute DOMString selectionDirection ; undefined setRangeText ( DOMString replacement ); undefined setRangeText ( DOMString replacement , unsigned long start , unsigned long end , optional SelectionMode selectionMode = preserve ); undefined setSelectionRange ( unsigned long start , unsigned long end , optional DOMString direction ); };

The textarea element represents a multiline plain text edit control for the element's raw value . The contents of the control represent the control's default value.

The raw value of a textarea control must be initially the empty string.

This element has rendering requirements involving the bidirectional algorithm .

The readonly attribute is a boolean attribute used to control whether the text can be edited by the user or not.

In this example, a text control is marked read-only because it represents a read-only file:

Filename: code /etc/bash.bashrc / code textarea name = buffer readonly # System-wide .bashrc file for interactive bash(1) shells. # To enable the settings / commands in this file for login shells as well, # this file has to be sourced in /etc/profile. # If not running interactively, don't do anything [ -z $PS1 ] && return / textarea

Constraint validation : If the readonly attribute is specified on a textarea element, the element is barred from constraint validation .

A textarea element is mutable if it is neither disabled nor has a readonly attribute specified.

When a textarea is mutable , its raw value should be editable by the user: the user agent should allow the user to edit, insert, and remove text, and to insert and remove line breaks in the form of U+000A LINE FEED (LF) characters. Any time the user causes the element's raw value to change, the user agent must queue an element task on the user interaction task source given the textarea element to fire an event named input at the textarea element, with the bubbles and composed attributes initialized to true. User agents may wait for a suitable break in the user's interaction before queuing the task; for example, a user agent could wait for the user to have not hit a key for 100ms, so as to only fire the event when the user pauses, instead of continuously for each keystroke.

A textarea element's dirty value flag must be set to true whenever the user interacts with the control in a way that changes the raw value .

The cloning steps for textarea elements must propagate the raw value and dirty value flag from the node being cloned to the copy.

The children changed steps for textarea elements must, if the element's dirty value flag is false, set the element's raw value to its child text content .

The reset algorithm for textarea elements is to set the user validity to false, dirty value flag back to false, and set the raw value of element to its child text content .

When a textarea element is popped off the stack of open elements of an HTML parser or XML parser , then the user agent must invoke the element's reset algorithm .

If the element is mutable , the user agent should allow the user to change the writing direction of the element, setting it either to a left-to-right writing direction or a right-to-left writing direction. If the user does so, the user agent must then run the following steps:

Set the element's dir attribute to " ltr " if the user selected a left-to-right writing direction, and " rtl " if the user selected a right-to-left writing direction.

Queue an element task on the user interaction task source given the textarea element to fire an event named input at the textarea element, with the bubbles and composed attributes initialized to true.

The cols attribute specifies the expected maximum number of characters per line. If the cols attribute is specified, its value must be a valid non-negative integer greater than zero. If applying the rules for parsing non-negative integers to the attribute's value results in a number greater than zero, then the element's character width is that value; otherwise, it is 20.

The user agent may use the textarea element's character width as a hint to the user as to how many characters the server prefers per line (e.g. for visual user agents by making the width of the control be that many characters). In visual renderings, the user agent should wrap the user's input in the rendering so that each line is no wider than this number of characters.

The rows attribute specifies the number of lines to show. If the rows attribute is specified, its value must be a valid non-negative integer greater than zero. If applying the rules for parsing non-negative integers to the attribute's value results in a number greater than zero, then the element's character height is that value; otherwise, it is 2.

Visual user agents should set the height of the control to the number of lines given by character height .

The wrap attribute is an enumerated attribute with the following keywords and states:

Keyword State Brief description soft Soft Text is not to be wrapped when submitted (though can still be wrapped in the rendering). hard Hard Text is to have newlines added by the user agent so that the text is wrapped when it is submitted.

The attribute's missing value default and invalid value default are both the Soft state.

If the element's wrap attribute is in the Hard state, the cols attribute must be specified.

For historical reasons, the element's value is normalized in three different ways for three different purposes. The raw value is the value as it was originally set. It is not normalized. The API value is the value used in the value IDL attribute, textLength IDL attribute, and by the maxlength and minlength content attributes. It is normalized so that line breaks use U+000A LINE FEED (LF) characters. Finally, there is the value , as used in form submission and other processing models in this specification. It is normalized as for the API value , and in addition, if necessary given the element's wrap attribute, additional line breaks are inserted to wrap the text at the given width.

The algorithm for obtaining the element's API value is to return the element's raw value , with newlines normalized .

The element's value is defined to be the element's API value with the textarea wrapping transformation applied. The textarea wrapping transformation is the following algorithm, as applied to a string:

If the element's wrap attribute is in the Hard state, insert U+000A LINE FEED (LF) characters into the string using an implementation-defined algorithm so that each line has no more than character width characters. For the purposes of this requirement, lines are delimited by the start of the string, the end of the string, and U+000A LINE FEED (LF) characters.

The maxlength attribute is a form control maxlength attribute .

If the textarea element has a maximum allowed value length , then the element's children must be such that the length of the value of the element's descendant text content with newlines normalized is less than or equal to the element's maximum allowed value length .

The minlength attribute is a form control minlength attribute .

The required attribute is a boolean attribute . When specified, the user will be required to enter a value before submitting the form.

Constraint validation : If the element has its required attribute specified, and the element is mutable , and the element's value is the empty string, then the element is suffering from being missing .

The placeholder attribute represents a short hint (a word or short phrase) intended to aid the user with data entry when the control has no value. A hint could be a sample value or a brief description of the expected format.

The placeholder attribute should not be used as an alternative to a label . For a longer hint or other advisory text, the title attribute is more appropriate.

These mechanisms are very similar but subtly different: the hint given by the control's label is shown at all times; the short hint given in the placeholder attribute is shown before the user enters a value; and the hint in the title attribute is shown when the user requests further help.

User agents should present this hint to the user when the element's value is the empty string and the control is not focused (e.g. by displaying it inside a blank unfocused control). All U+000D CARRIAGE RETURN U+000A LINE FEED character pairs (CRLF) in the hint, as well as all other U+000D CARRIAGE RETURN (CR) and U+000A LINE FEED (LF) characters in the hint, must be treated as line breaks when rendering the hint.

If a user agent normally doesn't show this hint to the user when the control is focused , then the user agent should nonetheless show the hint for the control if it was focused as a result of the autofocus attribute, since in that case the user will not have had an opportunity to examine the control before focusing it.

The name attribute represents the element's name. The dirname attribute controls how the element's directionality is submitted. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The form attribute is used to explicitly associate the textarea element with its form owner . The autocomplete attribute controls how the user agent provides autofill behavior.

textarea . type

Returns the string " textarea ". textarea . value

Returns the current value of the element.

Can be set, to change the value.

The cols , placeholder , required , rows , and wrap IDL attributes must reflect the respective content attributes of the same name. The cols and rows attributes are limited to only positive numbers with fallback . The cols IDL attribute's default value is 20. The rows IDL attribute's default value is 2. The dirName IDL attribute must reflect the dirname content attribute. The maxLength IDL attribute must reflect the maxlength content attribute, limited to only non-negative numbers . The minLength IDL attribute must reflect the minlength content attribute, limited to only non-negative numbers . The readOnly IDL attribute must reflect the readonly content attribute.

The type IDL attribute must return the value " textarea ".

The defaultValue attribute's getter must return the element's child text content .

The defaultValue attribute's setter must string replace all with the given value within this element.

The value IDL attribute must, on getting, return the element's API value . On setting, it must perform the following steps:

Let oldAPIValue be this element's API value .

Set this element's raw value to the new value.

Set this element's dirty value flag to true.

If the new API value is different from oldAPIValue , then move the text entry cursor position to the end of the text control, unselecting any selected text and resetting the selection direction to " none ".

The textLength IDL attribute must return the length of the element's API value .

The willValidate , validity , and validationMessage IDL attributes, and the checkValidity() , reportValidity() , and setCustomValidity() methods, are part of the constraint validation API . The labels IDL attribute provides a list of the element's label s. The select() , selectionStart , selectionEnd , selectionDirection , setRangeText() , and setSelectionRange() methods and IDL attributes expose the element's text selection. The disabled , form , and name IDL attributes are part of the element's forms API.

Here is an example of a textarea being used for unrestricted free-form text input in a form:

p If you have any comments, please let us know: textarea cols = 80 name = comments / textarea / p

To specify a maximum length for the comments, one can use the maxlength attribute:

p If you have any short comments, please let us know: textarea cols = 80 name = comments maxlength = 200 / textarea / p

To give a default value, text can be included inside the element:

p If you have any comments, please let us know: textarea cols = 80 name = comments You rock! / textarea / p

You can also give a minimum length. Here, a letter needs to be filled out by the user; a template (which is shorter than the minimum length) is provided, but is insufficient to submit the form:

textarea required minlength = 500 Dear Madam Speaker, Regarding your letter dated Yours Sincerely, / textarea

A placeholder can be given as well, to suggest the basic form to the user, without providing an explicit template:

textarea placeholder = Dear Francine, They closed the parks this week, so we won't be able to meet your there. Should we just have dinner? Love, Daddy / textarea

To have the browser submit the directionality of the element along with the value, the dirname attribute can be specified:

p If you have any comments, please let us know (you may use either English or Hebrew for your comments): textarea cols = 80 name = comments dirname = comments.dir / textarea / p

4.10.12 The output element

✔ MDN

Element/output

Support in all current engines. Firefox 4+ Safari 7+ Chrome 10+ Opera 11+ Edge 79+ Edge (Legacy) 18 Internet Explorer No Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 11+ ✔ MDN

HTMLOutputElement

Support in all current engines. Firefox 4+ Safari 5.1+ Chrome 9+ Opera 12.1+ Edge 79+ Edge (Legacy) 14+ Internet Explorer No Firefox Android ? Safari iOS ? Chrome Android ? WebView Android 3+ Samsung Internet ? Opera Android 12.1+ Categories : Flow content . Phrasing content . Listed , labelable , resettable , and autocapitalize-and-autocorrect inheriting form-associated element . Palpable content . Contexts in which this element can be used : Where phrasing content is expected. Content model : Phrasing content . Tag omission in text/html : Neither tag is omissible. Content attributes : Global attributes for — Specifies controls from which the output was calculated form — Associates the element with a form element name — Name of the element to use in the form.elements API. Accessibility considerations : For authors . For implementers . DOM interface : [ Exposed = Window ] interface HTMLOutputElement : HTMLElement { [ HTMLConstructor ] constructor (); [ SameObject , PutForwards = value ] readonly attribute DOMTokenList htmlFor ; readonly attribute HTMLFormElement ? form ; [ CEReactions ] attribute DOMString name ; readonly attribute DOMString type ; [ CEReactions ] attribute DOMString defaultValue ; [ CEReactions ] attribute DOMString value ; readonly attribute boolean willValidate ; readonly attribute ValidityState validity ; readonly attribute DOMString validationMessage ; boolean checkValidity (); boolean reportValidity (); undefined setCustomValidity ( DOMString error ); readonly attribute NodeList labels ; };

The output element represents the result of a calculation performed by the application, or the result of a user action.

This element can be contrasted with the samp element, which is the appropriate element for quoting the output of other programs run previously.

✔ MDN

Attributes/for

The for content attribute allows an explicit relationship to be made between the result of a calculation and the elements that represent the values that went into the calculation or that otherwise influenced the calculation. The for attribute, if specified, must contain a string consisting of an unordered set of unique space-separated tokens , none of which are identical to another token and each of which must have the value of an ID of an element in the same tree .

The form attribute is used to explicitly associate the output element with its form owner . The name attribute represents the element's name. The output element is associated with a form so that it can be easily referenced from the event handlers of form controls; the element's value itself is not submitted when the form is submitted.

The element has a default value override (null or a string). Initially it must be null.

The element's default value is determined by the following steps:

If this element's default value override is non-null, then return it.

Return this element's descendant text content .

The reset algorithm for output elements is to run these steps:

String replace all with this element's default value within this element.

Set this element's default value override to null. output . value [ = value ]

Returns the element's current value.

Can be set, to change the value.

output . defaultValue [ = value ]

Returns the element's current default value.

Can be set, to change the default value.

output . type

Returns the string " output ".

The value getter steps are to return this 's descendant text content .

The value setter steps are:

Set this 's default value override to its default value .

String replace all with the given value within this .

The defaultValue getter steps are to return the result of running this 's default value .

The defaultValue setter steps are:

If this 's default value override is null, then string replace all with the given value within this and return.

Set this 's default value override to the given value.

The type getter steps are to return " output ".

The htmlFor IDL attribute must reflect the for content attribute.

A simple calculator could use output for its display of calculated results:

form onsubmit = return false oninput = o.value = a.valueAsNumber + b.valueAsNumber input id = a type = number step = any + input id = b type = number step = any = output id = o for = a b / output / form

In this example, an output element is used to report the results of a calculation performed by a remote server, as they come in:

output id = result / output script var primeSource = new WebSocket ( 'ws://primes.example.net/' ); primeSource . onmessage = function ( event ) { document . getElementById ( 'result' ). value = event . data ; } / script

4.10.13 The progress element

✔ MDN

Element/progress

Support in all current engines. Firefox 6+ Safari 6+ Chrome 6+ Opera 11+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 10+ Firefox Android ? Safari iOS 7+ Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 11+ ✔ MDN

HTMLProgressElement

Support in all current engines. Firefox 6+ Safari 6+ Chrome 6+ Opera 12.1+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 10+ Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 12.1+ Categories : Flow content . Phrasing content . Labelable element . Palpable content . Contexts in which this element can be used : Where phrasing content is expected. Content model : Phrasing content , but there must be no progress element descendants. Tag omission in text/html : Neither tag is omissible. Content attributes : Global attributes value — Current value of the element max — Upper bound of range Accessibility considerations : For authors . For implementers . DOM interface : [ Exposed = Window ] interface HTMLProgressElement : HTMLElement { [ HTMLConstructor ] constructor (); [ CEReactions ] attribute double value ; [ CEReactions ] attribute double max ; readonly attribute double position ; readonly attribute NodeList labels ; };

The progress element represents the completion progress of a task. The progress is either indeterminate, indicating that progress is being made but that it is not clear how much more work remains to be done before the task is complete (e.g. because the task is waiting for a remote host to respond), or the progress is a number in the range zero to a maximum, giving the fraction of work that has so far been completed.

✔ MDN

Attributes/max

There are two attributes that determine the current task completion represented by the element. The value attribute specifies how much of the task has been completed, and the max attribute specifies how much work the task requires in total. The units are arbitrary and not specified.

To make a determinate progress bar, add a value attribute with the current progress (either a number from 0.0 to 1.0, or, if the max attribute is specified, a number from 0 to the value of the max attribute). To make an indeterminate progress bar, remove the value attribute.

Authors are encouraged to also include the current value and the maximum value inline as text inside the element, so that the progress is made available to users of legacy user agents.

Here is a snippet of a web application that shows the progress of some automated task:

section h2 Task Progress / h2 p Progress: progress id = p max = 100 span 0 / span % / progress / p script var progressBar = document . getElementById ( 'p' ); function updateProgress ( newValue ) { progressBar . value = newValue ; progressBar . getElementsByTagName ( 'span' )[ 0 ]. textContent = newValue ; } / script / section

(The updateProgress() method in this example would be called by some other code on the page to update the actual progress bar as the task progressed.)

The value and max attributes, when present, must have values that are valid floating-point numbers . The value attribute, if present, must have a value greater than or equal to zero, and less than or equal to the value of the max attribute, if present, or 1.0, otherwise. The max attribute, if present, must have a value greater than zero.

The progress element is the wrong element to use for something that is just a gauge, as opposed to task progress. For instance, indicating disk space usage using progress would be inappropriate. Instead, the meter element is available for such use cases.

User agent requirements : If the value attribute is omitted, then the progress bar is an indeterminate progress bar. Otherwise, it is a determinate progress bar.

If the progress bar is a determinate progress bar and the element has a max attribute, the user agent must parse the max attribute's value according to the rules for parsing floating-point number values . If this does not result in an error, and if the parsed value is greater than zero, then the maximum value of the progress bar is that value. Otherwise, if the element has no max attribute, or if it has one but parsing it resulted in an error, or if the parsed value was less than or equal to zero, then the maximum value of the progress bar is 1.0.

If the progress bar is a determinate progress bar, user agents must parse the value attribute's value according to the rules for parsing floating-point number values . If this does not result in an error and the parsed value is greater than zero, then the value of the progress bar is that parsed value. Otherwise, if parsing the value attribute's value resulted in an error or a number less than or equal to zero, then the value of the progress bar is zero.

If the progress bar is a determinate progress bar, then the current value is the maximum value , if value is greater than the maximum value , and value otherwise.

UA requirements for showing the progress bar : When representing a progress element to the user, the UA should indicate whether it is a determinate or indeterminate progress bar, and in the former case, should indicate the relative position of the current value relative to the maximum value .

progress . position

For a determinate progress bar (one with known current and maximum values), returns the result of dividing the current value by the maximum value.

For an indeterminate progress bar, returns −1.

If the progress bar is an indeterminate progress bar, then the position IDL attribute must return −1. Otherwise, it must return the result of dividing the current value by the maximum value .

If the progress bar is an indeterminate progress bar, then the value IDL attribute, on getting, must return 0. Otherwise, it must return the current value . On setting, the given value must be converted to the best representation of the number as a floating-point number and then the value content attribute must be set to that string.

Setting the value IDL attribute to itself when the corresponding content attribute is absent would change the progress bar from an indeterminate progress bar to a determinate progress bar with no progress.

The max IDL attribute must reflect the content attribute of the same name, limited to only positive numbers . The default value for max is 1.0.

The labels IDL attribute provides a list of the element's label s.

4.10.14 The meter element

✔ MDN

Element/meter

Support in all current engines. Firefox 16+ Safari 6+ Chrome 6+ Opera 11+ Edge 79+ Edge (Legacy) 18 Internet Explorer No Firefox Android ? Safari iOS 10.3+ Chrome Android ? WebView Android No Samsung Internet ? Opera Android 11+ ✔ MDN

HTMLMeterElement

Support in all current engines. Firefox 16+ Safari 6+ Chrome 6+ Opera 11+ Edge 79+ Edge (Legacy) 12+ Internet Explorer No Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 11+ Categories : Flow content . Phrasing content . Labelable element . Palpable content . Contexts in which this element can be used : Where phrasing content is expected. Content model : Phrasing content , but there must be no meter element descendants. Tag omission in text/html : Neither tag is omissible. Content attributes : Global attributes value — Current value of the element min — Lower bound of range max — Upper bound of range low — High limit of low range high — Low limit of high range optimum — Optimum value in gauge Accessibility considerations : For authors . For implementers . DOM interface : [ Exposed = Window ] interface HTMLMeterElement : HTMLElement { [ HTMLConstructor ] constructor (); [ CEReactions ] attribute double value ; [ CEReactions ] attribute double min ; [ CEReactions ] attribute double max ; [ CEReactions ] attribute double low ; [ CEReactions ] attribute double high ; [ CEReactions ] attribute double optimum ; readonly attribute NodeList labels ; };

The meter element represents a scalar measurement within a known range, or a fractional value; for example disk usage, the relevance of a query result, or the fraction of a voting population to have selected a particular candidate.

This is also known as a gauge.

The meter element should not be used to indicate progress (as in a progress bar). For that role, HTML provides a separate progress element.

The meter element also does not represent a scalar value of arbitrary range — for example, it would be wrong to use this to report a weight, or height, unless there is a known maximum value.

There are six attributes that determine the semantics of the gauge represented by the element.

✔ MDN

Attributes/max

Attributes/min

The min attribute specifies the lower bound of the range, and the max attribute specifies the upper bound. The value attribute specifies the value to have the gauge indicate as the "measured" value.

The other three attributes can be used to segment the gauge's range into "low", "medium", and "high" parts, and to indicate which part of the gauge is the "optimum" part. The low attribute specifies the range that is considered to be the "low" part, and the high attribute specifies the range that is considered to be the "high" part. The optimum attribute gives the position that is "optimum"; if that is higher than the "high" value then this indicates that the higher the value, the better; if it's lower than the "low" mark then it indicates that lower values are better, and naturally if it is in between then it indicates that neither high nor low values are good.

Authoring requirements : The value attribute must be specified. The value , min , low , high , max , and optimum attributes, when present, must have values that are valid floating-point numbers .

In addition, the attributes' values are further constrained:

Let value be the value attribute's number.

If the min attribute is specified, then let minimum be that attribute's value; otherwise, let it be zero.

If the max attribute is specified, then let maximum be that attribute's value; otherwise, let it be 1.0.

The following inequalities must hold, as applicable:

minimum ≤ value ≤ maximum

minimum ≤ low ≤ maximum (if low is specified)

minimum ≤ high ≤ maximum (if high is specified)

minimum ≤ optimum ≤ maximum (if optimum is specified)

low ≤ high (if both low and high are specified)

If no minimum or maximum is specified, then the range is assumed to be 0..1, and the value thus has to be within that range.

Authors are encouraged to include a textual representation of the gauge's state in the element's contents, for users of user agents that do not support the meter element.

When used with microdata , the meter element's value attribute provides the element's machine-readable value.

The following examples show three gauges that would all be three-quarters full:

Storage space usage: meter value = 6 max = 8 6 blocks used (out of 8 total) / meter Voter turnout: meter value = 0.75 img alt = 75% src = graph75.png / meter Tickets sold: meter min = 0 max = 100 value = 75 / meter

The following example is incorrect use of the element, because it doesn't give a range (and since the default maximum is 1, both of the gauges would end up looking maxed out):

p The grapefruit pie had a radius of meter value = 12 12cm / meter and a height of meter value = 2 2cm / meter . / p !-- BAD! --

Instead, one would either not include the meter element, or use the meter element with a defined range to give the dimensions in context compared to other pies:

p The grapefruit pie had a radius of 12cm and a height of 2cm. / p dl dt Radius: dd meter min = 0 max = 20 value = 12 12cm / meter dt Height: dd meter min = 0 max = 10 value = 2 2cm / meter / dl

There is no explicit way to specify units in the meter element, but the units may be specified in the title attribute in free-form text.

The example above could be extended to mention the units:

dl dt Radius: dd meter min = 0 max = 20 value = 12 title = centimeters 12cm / meter dt Height: dd meter min = 0 max = 10 value = 2 title = centimeters 2cm / meter / dl

User agent requirements : User agents must parse the min , max , value , low , high , and optimum attributes using the rules for parsing floating-point number values .

User agents must then use all these numbers to obtain values for six points on the gauge, as follows. (The order in which these are evaluated is important, as some of the values refer to earlier ones.)

The minimum value

If the min attribute is specified and a value could be parsed out of it, then the minimum value is that value. Otherwise, the minimum value is zero.

The maximum value

If the max attribute is specified and a value could be parsed out of it, then the candidate maximum value is that value. Otherwise, the candidate maximum value is 1.0.

If the candidate maximum value is greater than or equal to the minimum value, then the maximum value is the candidate maximum value. Otherwise, the maximum value is the same as the minimum value.

The actual value

If the value attribute is specified and a value could be parsed out of it, then that value is the candidate actual value. Otherwise, the candidate actual value is zero.

If the candidate actual value is less than the minimum value, then the actual value is the minimum value.

Otherwise, if the candidate actual value is greater than the maximum value, then the actual value is the maximum value.

Otherwise, the actual value is the candidate actual value.

The low boundary

If the low attribute is specified and a value could be parsed out of it, then the candidate low boundary is that value. Otherwise, the candidate low boundary is the same as the minimum value.

If the candidate low boundary is less than the minimum value, then the low boundary is the minimum value.

Otherwise, if the candidate low boundary is greater than the maximum value, then the low boundary is the maximum value.

Otherwise, the low boundary is the candidate low boundary.

The high boundary

If the high attribute is specified and a value could be parsed out of it, then the candidate high boundary is that value. Otherwise, the candidate high boundary is the same as the maximum value.

If the candidate high boundary is less than the low boundary, then the high boundary is the low boundary.

Otherwise, if the candidate high boundary is greater than the maximum value, then the high boundary is the maximum value.

Otherwise, the high boundary is the candidate high boundary.

The optimum point

If the optimum attribute is specified and a value could be parsed out of it, then the candidate optimum point is that value. Otherwise, the candidate optimum point is the midpoint between the minimum value and the maximum value.

If the candidate optimum point is less than the minimum value, then the optimum point is the minimum value.

Otherwise, if the candidate optimum point is greater than the maximum value, then the optimum point is the maximum value.

Otherwise, the optimum point is the candidate optimum point.

All of which will result in the following inequalities all being true:

minimum value ≤ actual value ≤ maximum value

minimum value ≤ low boundary ≤ high boundary ≤ maximum value

minimum value ≤ optimum point ≤ maximum value

UA requirements for regions of the gauge : If the optimum point is equal to the low boundary or the high boundary, or anywhere in between them, then the region between the low and high boundaries of the gauge must be treated as the optimum region, and the low and high parts, if any, must be treated as suboptimal. Otherwise, if the optimum point is less than the low boundary, then the region between the minimum value and the low boundary must be treated as the optimum region, the region from the low boundary up to the high boundary must be treated as a suboptimal region, and the remaining region must be treated as an even less good region. Finally, if the optimum point is higher than the high boundary, then the situation is reversed; the region between the high boundary and the maximum value must be treated as the optimum region, the region from the high boundary down to the low boundary must be treated as a suboptimal region, and the remaining region must be treated as an even less good region.

UA requirements for showing the gauge : When representing a meter element to the user, the UA should indicate the relative position of the actual value to the minimum and maximum values, and the relationship between the actual value and the three regions of the gauge.

The following markup:

h3 Suggested groups / h3 menu li a href = ?cmd=hsg onclick = hideSuggestedGroups() Hide suggested groups / a / li / menu ul li p a href = /group/comp.infosystems.www.authoring.stylesheets/view comp.infosystems.www.authoring.stylesheets / a - a href = /group/comp.infosystems.www.authoring.stylesheets/subscribe join / a / p p Group description: strong Layout/presentation on the WWW. / strong / p p meter value = 0.5 Moderate activity, / meter Usenet, 618 subscribers / p / li li p a href = /group/netscape.public.mozilla.xpinstall/view netscape.public.mozilla.xpinstall / a - a href = /group/netscape.public.mozilla.xpinstall/subscribe join / a / p p Group description: strong Mozilla XPInstall discussion. / strong / p p meter value = 0.25 Low activity, / meter Usenet, 22 subscribers / p / li li p a href = /group/mozilla.dev.general/view mozilla.dev.general / a - a href = /group/mozilla.dev.general/subscribe join / a / p p meter value = 0.25 Low activity, / meter Usenet, 66 subscribers / p / li / ul

Might be rendered as follows:

User agents may combine the value of the title attribute and the other attributes to provide context-sensitive help or inline text detailing the actual values.

For example, the following snippet:

meter min = 0 max = 60 value = 23.2 title = seconds / meter

might cause the user agent to display a gauge with a tooltip saying "Value: 23.2 out of 60." on one line and "seconds" on a second line.

The value IDL attribute, on getting, must return the actual value . On setting, the given value must be converted to the best representation of the number as a floating-point number and then the value content attribute must be set to that string.

The min IDL attribute, on getting, must return the minimum value . On setting, the given value must be converted to the best representation of the number as a floating-point number and then the min content attribute must be set to that string.

The max IDL attribute, on getting, must return the maximum value . On setting, the given value must be converted to the best representation of the number as a floating-point number and then the max content attribute must be set to that string.

The low IDL attribute, on getting, must return the low boundary . On setting, the given value must be converted to the best representation of the number as a floating-point number and then the low content attribute must be set to that string.

The high IDL attribute, on getting, must return the high boundary . On setting, the given value must be converted to the best representation of the number as a floating-point number and then the high content attribute must be set to that string.

The optimum IDL attribute, on getting, must return the optimum value . On setting, the given value must be converted to the best representation of the number as a floating-point number and then the optimum content attribute must be set to that string.

The labels IDL attribute provides a list of the element's label s.

The following example shows how a gauge could fall back to localized or pretty-printed text.

p Disk usage: meter min = 0 value = 170261928 max = 233257824 170 261 928 bytes used out of 233 257 824 bytes available / meter / p

4.10.15 The fieldset element

✔ MDN

Element/fieldset

HTMLFieldSetElement

The fieldset element represents a set of form controls (or other content) grouped together, optionally with a caption. The caption is given by the first legend element that is a child of the fieldset element, if any. The remainder of the descendants form the group.

✔ MDN

Element/fieldset#attr-disabled

Support in all current engines. Firefox 4+ Safari 6+ Chrome 20+ Opera 12+ Edge 79+ Edge (Legacy) 12+ Internet Explorer Yes Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 12+

The disabled attribute, when specified, causes all the form control descendants of the fieldset element, excluding those that are descendants of the fieldset element's first legend element child, if any, to be disabled .

A fieldset element is a disabled fieldset if it matches any of the following conditions:

Its disabled attribute is specified It is a descendant of another fieldset element whose disabled attribute is specified, and is not a descendant of that fieldset element's first legend element child, if any.

The form attribute is used to explicitly associate the fieldset element with its form owner . The name attribute represents the element's name.

fieldset . type

Returns the string "fieldset". fieldset . elements

Returns an HTMLCollection of the form controls in the element.

The disabled IDL attribute must reflect the content attribute of the same name.

The type IDL attribute must return the string " fieldset ".

The elements IDL attribute must return an HTMLCollection rooted at the fieldset element, whose filter matches listed elements .

The willValidate , validity , and validationMessage attributes, and the checkValidity() , reportValidity() , and setCustomValidity() methods, are part of the constraint validation API . The form and name IDL attributes are part of the element's forms API.

This example shows a fieldset element being used to group a set of related controls:

fieldset legend Display / legend p label input type = radio name = c value = 0 checked Black on White / label p label input type = radio name = c value = 1 White on Black / label p label input type = checkbox name = g Use grayscale / label p label Enhance contrast input type = range name = e list = contrast min = 0 max = 100 value = 0 step = 1 / label datalist id = contrast option label = Normal value = 0 option label = Maximum value = 100 / datalist / fieldset

The following snippet shows a fieldset with a checkbox in the legend that controls whether or not the fieldset is enabled. The contents of the fieldset consist of two required text controls and an optional year/month control.

fieldset name = clubfields disabled legend label input type = checkbox name = club onchange = form.clubfields.disabled = !checked Use Club Card / label / legend p label Name on card: input name = clubname required / label / p p label Card number: input name = clubnum required pattern = [-0-9]+ / label / p p label Expiry date: input name = clubexp type = month / label / p / fieldset

You can also nest fieldset elements. Here is an example expanding on the previous one that does so:

fieldset name = clubfields disabled legend label input type = checkbox name = club onchange = form.clubfields.disabled = !checked Use Club Card / label / legend p label Name on card: input name = clubname required / label / p fieldset name = numfields legend label input type = radio checked name = clubtype onchange = form.numfields.disabled = !checked My card has numbers on it / label / legend p label Card number: input name = clubnum required pattern = [-0-9]+ / label / p / fieldset fieldset name = letfields disabled legend label input type = radio name = clubtype onchange = form.letfields.disabled = !checked My card has letters on it / label / legend p label Card code: input name = clublet required pattern = [A-Za-z]+ / label / p / fieldset / fieldset

In this example, if the outer "Use Club Card" checkbox is not checked, everything inside the outer fieldset , including the two radio buttons in the legends of the two nested fieldset s, will be disabled. However, if the checkbox is checked, then the radio buttons will both be enabled and will let you select which of the two inner fieldset s is to be enabled.

This example shows a grouping of controls where the legend element both labels the grouping, and the nested heading element surfaces the grouping in the document outline:

fieldset legend h2 How can we best reach you? / h2 / legend p label input type = radio checked name = contact_pref Phone / label / p p label input type = radio name = contact_pref Text / label / p p label input type = radio name = contact_pref Email / label / p / fieldset

4.10.16 The legend element

✔ MDN

Element/legend

HTMLLegendElement

Support in all current engines. Firefox 1+ Safari 1+ Chrome 1+ Opera 12.1+ Edge 79+ Edge (Legacy) 12+ Internet Explorer 6+ Firefox Android ? Safari iOS ? Chrome Android ? WebView Android ? Samsung Internet ? Opera Android 12.1+ Categories : None. Contexts in which this element can be used : As the first child of a fieldset element. Content model : Phrasing content , optionally intermixed with heading content . Tag omission in text/html : Neither tag is omissible. Content attributes : Global attributes Accessibility considerations : For authors . For implementers . DOM interface : [ Exposed = Window ] interface HTMLLegendElement : HTMLElement { [ HTMLConstructor ] constructor (); readonly attribute HTMLFormElement ? form ; // also has obsolete members };

The legend element represents a caption for the rest of the contents of the legend element's parent fieldset element, if any.

legend . form

Returns the element's form element, if any, or null otherwise.

The form IDL attribute's behavior depends on whether the legend element is in a fieldset element or not. If the legend has a fieldset element as its parent, then the form IDL attribute must return the same value as the form IDL attribute on that fieldset element. Otherwise, it must return null.

← 4.10.5 The input element — Table of Contents — 4.10.17 Form control infrastructure →

button

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HTML Standard

HTML

4.10.6 The button element

4.10.7 The select element

4.10.8 The datalist element

4.10.9 The optgroup element

4.10.10 The option element

4.10.11 The textarea element

4.10.12 The output element

4.10.13 The progress element

4.10.14 The meter element

4.10.15 The fieldset element

4.10.16 The legend element

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