HTML

Living Standard — Last Updated 14 September 2017

1. 1. 1. 4.10.6 The button element
      2. 4.10.7 The select element
      3. 4.10.8 The datalist element
      4. 4.10.9 The optgroup element
      5. 4.10.10 The option element
      6. 4.10.11 The textarea element
      7. 4.10.12 The output element
      8. 4.10.13 The progress element
      9. 4.10.14 The meter element
      10. 4.10.15 The fieldset element
      11. 4.10.16 The legend element

4.10.6 The button element

Categories:

Flow content.

Phrasing content.

Interactive content.

Listed, labelable, and submittable 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.

Tag omission in text/html:

Neither tag is omissible.

Content attributes:

Global attributes

autofocus — Automatically focus the form control when the page is loaded

disabled — Whether the form control is disabled

form — Associates the control with a form element

formaction — URL to use for form submission

formenctype — Form data set encoding type to use for form submission

formmethod — HTTP method to use for form submission

formnovalidate — Bypass form control validation for form submission

formtarget — Browsing context for form submission

name — Name of form control to use for form submission and in the form.elements API

type — Type of button

value — Value to be used for form submission

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLButtonElement : HTMLElement {
  [CEReactions] attribute boolean autofocus;
  [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();
  void setCustomValidity(DOMString error);

  readonly attribute NodeList labels;
};

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. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

The missing value default is 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's activation behavior is to run the steps defined in the following list for the current state of this element's type attribute, if this element is not disabled, and do nothing otherwise:

Submit Button

If the element has a form owner and the element's node document is fully active, the element must submit the form owner from the button element.

Reset Button

If the element has a form owner and the element's node document is fully active, the element must reset the form owner.

Button

Do nothing.

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 autofocus attribute controls focus. 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 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 labels. The autofocus, disabled, form, and name IDL attributes are part of the element's forms API.

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

4.10.7 The select element

Categories:

Flow content.

Phrasing content.

Interactive content.

Listed, labelable, submittable, and resettable 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, and script-supporting elements.

Tag omission in text/html:

Neither tag is omissible.

Content attributes:

Global attributes

autocomplete — Hint for form autofill feature

autofocus — Automatically focus the form control when the page is loaded

disabled — Whether the form control is disabled

form — Associates the control with a form element

multiple — Whether to allow multiple values

name — Name of form control 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

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLSelectElement : HTMLElement {
  [CEReactions] attribute DOMString autocomplete;
  [CEReactions] attribute boolean autofocus;
  [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 Element? item(unsigned long index);
  HTMLOptionElement? namedItem(DOMString name);
  [CEReactions] void add((HTMLOptionElement or HTMLOptGroupElement) element, optional (HTMLElement or long)? before = null);
  [CEReactions] void remove(); // ChildNode overload
  [CEReactions] void remove(long index);
  [CEReactions] setter void (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();
  void setCustomValidity(DOMString error);

  readonly attribute NodeList labels;
};

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

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.

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.

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.

If nodes are inserted or nodes are removed causing the list of options to gain or lose one or more option elements, or if an option element in the list of options asks for a reset, then, if the select element's multiple attribute is absent, the user agent must run the first applicable set of steps from the following list:

If the select element's display size is 1, and no option elements in the select element's list of options have their selectedness set to true

Set the selectedness of the first option element in the list of options in tree order that is not disabled, if any, to true.

If two or more option elements in the select element's list of options have their selectedness set to true

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.

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 a task, using the user interaction task source, to run these steps:

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

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

The reset algorithm for select elements is to go through all the option elements in the element's list of options, set their selectedness to true if the option element has a selected attribute, and false otherwise, set their dirtiness to false, and then have the option elements ask for a reset.

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 autofocus attribute controls focus. The autocomplete attribute controls how the user agent provides autofill behavior.

A select element that is not disabled is mutable.

select . type

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

select . 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)

select[index]

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

element = select . namedItem(name)

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 ] )

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

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

select . selectedIndex [ = value ]

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.

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() method must act like its namesake method on that same options collection.

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 zero.

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 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 labels. The autofocus, disabled, form, and name IDL attributes are part of the element's forms API.

<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>

<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>

<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>

<p>Select the songs from that you would like on your Act II Mix Tape:</p>
<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>

4.10.8 The datalist element

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

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLDataListElement : HTMLElement {
  [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>
 Sex:
 <input name=sex list=sexes>
 <datalist id=sexes>
  <option value="Female">
  <option value="Male">
 </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>
 Sex:
 <input name=sex list=sexes>
</label>
<datalist id=sexes>
 <label>
  or select from the list:
  <select name=sex>
   <option value="">
   <option>Female
   <option>Male
  </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

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, 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

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLOptGroupElement : HTMLElement {
  [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.

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.

<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 Magnestism">
    <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

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, or if it is immediately followed by an optgroup 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

DOM interface:

[Exposed=Window,
 HTMLConstructor,
 NamedConstructor=Option(optional DOMString text = "", optional DOMString value, optional boolean defaultSelected = false, optional boolean selected = false)]
interface HTMLOptionElement : HTMLElement {
  [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.

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 ] ] ] ] )

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.

On setting, the text attribute must act as if the textContent IDL attribute on the element had been set to the new value.

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 constructor 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 constructor must perform the following steps:

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

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

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

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

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

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

7. Return option.

4.10.11 The textarea element

Categories:

Flow content.

Phrasing content.

Interactive content.

Listed, labelable, submittable, and resettable 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

autofocus — Automatically focus the form control when the page is loaded

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 control with a form element

inputmode — Hint for selecting an input modality

maxlength — Maximum length of value

minlength — Minimum length of value

name — Name of form control 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

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLTextAreaElement : HTMLElement {
  [CEReactions] attribute DOMString autocomplete;
  [CEReactions] attribute boolean autofocus;
  [CEReactions] attribute unsigned long cols;
  [CEReactions] attribute DOMString dirName;
  [CEReactions] attribute boolean disabled;
  readonly attribute HTMLFormElement? form;
  [CEReactions] attribute DOMString inputMode;
  [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;
  [CEReactions] attribute [TreatNullAs=EmptyString] DOMString value;
  readonly attribute unsigned long textLength;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  boolean reportValidity();
  void setCustomValidity(DOMString error);

  readonly attribute NodeList labels;

  void select();
  attribute unsigned long selectionStart;
  attribute unsigned long selectionEnd;
  attribute DOMString selectionDirection;
  void setRangeText(DOMString replacement);
  void setRangeText(DOMString replacement, unsigned long start, unsigned long end, optional SelectionMode selectionMode = "preserve");
  void 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.

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" ] &amp;&amp; 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 a task to fire an event named input at the textarea element, with the bubbles attribute 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 child text content change 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 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:

1. 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.

2. Queue a task to fire an event named input at the textarea element, with the bubbles attribute 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 two keywords and states: the soft keyword which maps to the Soft state, and the hard keyword which maps to the Hard state. The missing value default is the Soft state.

The Soft state indicates that the text in the textarea is not to be wrapped when it is submitted (though it can still be wrapped in the rendering).

The Hard state indicates that the text in the textarea is to have newlines added by the user agent so that the text is wrapped when it is submitted.

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 so that line breaks use U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pairs, 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 the textarea line break normalization transformation applied. The textarea line break normalization transformation is the following algorithm, as applied to a string:

1. Replace every U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pair with a single U+000A LINE FEED (LF) character.

2. Replace every remaining U+000D CARRIAGE RETURN character with a single U+000A LINE FEED (LF) character.

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

1. Replace every occurrence of a U+000D CARRIAGE RETURN (CR) character not followed by a U+000A LINE FEED (LF) character, and every occurrence of a U+000A LINE FEED (LF) character not preceded by a U+000D CARRIAGE RETURN (CR) character, by a two-character string consisting of a U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pair.

2. If the element's wrap attribute is in the Hard state, insert U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pairs into the string using a UA-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+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pairs.

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 JavaScript string length of the value of the element's textContent IDL attribute with the textarea line break normalization transformation applied is equal to or less than 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.

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 autofocus attribute controls focus. The inputmode attribute controls the user interface's input modality for the control. 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 non-negative numbers greater than zero 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 inputMode IDL attribute must reflect the inputmode content attribute, limited to only known values. 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 IDL attribute must, on getting, return the element's child text content. On setting, it must act as the setter for the element's textContent IDL attribute.

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

1. Let oldAPIValue be this element's API value.

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

3. Set this element's dirty value flag to true.

4. 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 JavaScript string 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 labels. The select(), selectionStart, selectionEnd, selectionDirection, setRangeText(), and setSelectionRange() methods and IDL attributes expose the element's text selection. The autofocus, disabled, form, and name IDL attributes are part of the element's forms API.

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

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

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

<textarea required minlength="500">Dear Madam Speaker,

Regarding your letter dated ...

...

Yours Sincerely,

...</textarea>

<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>

<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

Categories:

Flow content.

Phrasing content.

Listed, labelable, and resettable 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 control with a form element

name — Name of form control to use in the form.elements API

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLOutputElement : HTMLElement {
  [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();
  void 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.

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 that are case-sensitive, 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 value mode flag which is either value or default. Initially, the value mode flag must be set to default.

The element also has a default value. Initially, the default value must be the empty string.

When the value mode flag is in mode default, the contents of the element represent both the value of the element and its default value. When the value mode flag is in mode value, the contents of the element represent the value of the element only, and the default value is only accessible using the defaultValue IDL attribute.

Whenever the element's descendants are changed in any way, if the value mode flag is in mode default, the element's default value must be set to the value of the element's textContent IDL attribute.

The reset algorithm for output elements is to set the element's value mode flag to default and then to set the element's textContent IDL attribute to the value of the element's default value (thus replacing the element's child nodes).

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 IDL attribute must act like the element's textContent IDL attribute, except that on setting, in addition, before the child nodes are changed, the element's value mode flag must be set to value.

The defaultValue IDL attribute, on getting, must return the element's default value. On setting, the attribute must set the element's default value, and, if the element's value mode flag is in the mode default, set the element's textContent IDL attribute as well.

The type attribute must return the string "output".

The htmlFor IDL attribute must reflect the for content attribute.

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 labels. The form and name IDL attributes are part of the element's forms API.

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

<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

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

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLProgressElement : HTMLElement {
  [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.

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.

<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 value and max attributes, when present, must have values that are valid floating-point numbers. The value attribute, if present, must have a value equal to or greater than 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 if the parsed value is less than the maximum value and greater than zero, then the current value of the progress bar is that parsed value. Otherwise, if the parsed value was greater than or equal to the maximum value, then the current value of the progress bar is the maximum value of the progress bar. Otherwise, if parsing the value attribute's value resulted in an error, or a number less than or equal to zero, then the current value of the progress bar is zero.

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 numbers greater than zero. The default value for max is 1.0.

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

4.10.14 The meter element

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

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLMeterElement : HTMLElement {
  [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.

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.

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>

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

<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.

<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.

<h3>Suggested groups</h3>
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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.

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

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 labels.

<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

Categories:

Flow content.

Sectioning root.

Listed form-associated element.

Palpable content.

Contexts in which this element can be used:

Where flow content is expected.

Content model:

Optionally a legend element, followed by flow content.

Tag omission in text/html:

Neither tag is omissible.

Content attributes:

Global attributes

disabled — Whether the form control is disabled

form — Associates the control with a form element

name — Name of form control to use in the form.elements API

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLFieldSetElement : HTMLElement {
  [CEReactions] attribute boolean disabled;
  readonly attribute HTMLFormElement? form;
  [CEReactions] attribute DOMString name;

  readonly attribute DOMString type;

  [SameObject] readonly attribute HTMLCollection elements;

  readonly attribute boolean willValidate;
  [SameObject] readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  boolean reportValidity();
  void setCustomValidity(DOMString error);
};

The fieldset element represents a set of form controls optionally grouped under a common name.

The name of the group 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.

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.

<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>

<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>

<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>

4.10.16 The legend element

Categories:

None.

Contexts in which this element can be used:

As the first child of a fieldset element.

Content model:

Phrasing content.

Tag omission in text/html:

Neither tag is omissible.

Content attributes:

Global attributes

DOM interface:

[Exposed=Window,
 HTMLConstructor]
interface HTMLLegendElement : HTMLElement {
  readonly attribute HTMLFormElement? form;
};

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.