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4.10.9 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 or optgroup elements.
Content attributes:
Global attributes
autofocus
disabled
form
multiple
name
required
size
DOM interface:
interface HTMLSelectElement : HTMLElement {
           attribute boolean autofocus;
           attribute boolean disabled;
  readonly attribute HTMLFormElement? form;
           attribute boolean multiple;
           attribute DOMString name;
           attribute boolean required;
           attribute unsigned long size;

  readonly attribute DOMString type;

  readonly attribute HTMLOptionsCollection options;
           attribute unsigned long length;
  getter Element item(unsigned long index);
  object namedItem(DOMString name);
  void add((HTMLOptionElement or HTMLOptGroupElement) element, optional (HTMLElement or long)? before = null);
  void remove(long index);
  setter creator void (unsigned long index, HTMLOptionElement option);

  readonly attribute HTMLCollection selectedOptions;
           attribute long selectedIndex;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  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.

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 and then queue a task to fire a simple event that bubbles named change at the select element, using the user interaction task source as the task source.

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 element 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 and then queue a task to fire a simple event that bubbles named change at the select element, using the user interaction task source as the task source.

If the multiple attribute is absent and the element's display size is 1, then whenever there are no option elements in the select element's list of options that have their selectedness set to true, the user agent must 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 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 (either through a click, or through a menu command, or any other mechanism). Upon the selectedness of one or more option elements being changed by the user, and before the relevant user interaction event is queued (e.g. before a related click event), the user agent must queue a task to fire a simple event that bubbles named change at the select element, using the user interaction task source as the task source.

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

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.

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

If there are multiple matching items, then a NodeList object containing all those elements is returned.

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 exception 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 for a given property index index to a new value value, it must instead set the value of a new indexed property with the given property index index to the new value value on the options collection.

Similarly, the add() and remove() methods must act like their namesake methods on that same options collection.

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.

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.

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 attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API. The labels 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.

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 he 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.

<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>