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---
title: HTMLSelectElement
slug: Web/API/HTMLSelectElement
translation_of: Web/API/HTMLSelectElement
---
<div>{{APIRef("HTML DOM")}}</div>
<p><code><strong>HTMLSelectElement</strong></code> 介面代表了 {{HTMLElement("select")}} HTML 元素。此介面也自 {{domxref("HTMLElement")}} 介面繼承了所有 HTML 元素的屬性及方法。</p>
<p>{{InheritanceDiagram(600, 120)}}</p>
<h2 id="屬性">屬性</h2>
<p><em>This interface inherits the properties of {{domxref("HTMLElement")}}, and of {{domxref("Element")}} and {{domxref("Node")}}.</em></p>
<dl>
<dt>{{domxref("HTMLSelectElement.autofocus")}}</dt>
<dd>A {{jsxref("Boolean")}} reflecting the {{htmlattrxref("autofocus", "select")}} HTML attribute, which indicates whether the control should have input focus when the page loads, unless the user overrides it, for example by typing in a different control. Only one form-associated element in a document can have this attribute specified. {{gecko_minversion_inline("2.0")}}</dd>
<dt>{{domxref("HTMLSelectElement.disabled")}}</dt>
<dd>A {{jsxref("Boolean")}} reflecting the {{htmlattrxref("disabled", "select")}} HTML attribute, which indicates whether the control is disabled. If it is disabled, it does not accept clicks.</dd>
<dt>{{domxref("HTMLSelectElement.form")}}{{ReadOnlyInline}}</dt>
<dd>An {{domxref("HTMLFormElement")}} referencing the form that this element is associated with. If the element is not associated with of a {{HTMLElement("form")}} element, then it returns <code>null</code>.</dd>
<dt>{{domxref("HTMLSelectElement.labels")}}{{ReadOnlyInline}}</dt>
<dd>A {{domxref("NodeList")}} of {{HTMLElement("label")}} elements associated with the element.</dd>
<dt>{{domxref("HTMLSelectElement.length")}}</dt>
<dd>An <code>unsigned long </code>The number of {{HTMLElement("option")}} elements in this <code>select</code> element.</dd>
<dt>{{domxref("HTMLSelectElement.multiple")}}</dt>
<dd>A {{jsxref("Boolean")}} reflecting the {{htmlattrxref("multiple", "select")}} HTML attribute, which indicates whether multiple items can be selected.</dd>
<dt>{{domxref("HTMLSelectElement.name")}}</dt>
<dd>A {{domxref("DOMString")}} reflecting the {{htmlattrxref("name", "select")}} HTML attribute, containing the name of this control used by servers and DOM search functions.</dd>
<dt>{{domxref("HTMLSelectElement.options")}}{{ReadOnlyInline}}</dt>
<dd>An {{domxref("HTMLOptionsCollection")}} representing the set of {{HTMLElement("option")}} elements contained by this element.</dd>
<dt>{{domxref("HTMLSelectElement.required")}}</dt>
<dd>A {{jsxref("Boolean")}} reflecting the {{htmlattrxref("required", "select")}} HTML attribute, which indicates whether the user is required to select a value before submitting the form. {{gecko_minversion_inline("2.0")}}</dd>
<dt>{{domxref("HTMLSelectElement.selectedIndex")}}</dt>
<dd>A <code>long</code> reflecting the index of the first selected {{HTMLElement("option")}} element. The value <code>-1</code> indicates no element is selected.</dd>
<dt>{{domxref("HTMLSelectElement.selectedOptions")}}{{ReadOnlyInline}}</dt>
<dd>An {{domxref("HTMLCollection")}} representing the set of {{HTMLElement("option")}} elements that are selected.</dd>
<dt>{{domxref("HTMLSelectElement.size")}}</dt>
<dd>A <code>long</code> reflecting the {{htmlattrxref("size", "select")}} HTML attribute, which contains the number of visible items in the control. The default is 1, unless <code>multiple</code> is true, in which case it is 4.</dd>
<dt>{{domxref("HTMLSelectElement.type")}}{{ReadOnlyInline}}</dt>
<dd>A {{domxref("DOMString")}} represeting the form control's type. When <code>multiple</code> is <code>true</code>, it returns <code>"select-multiple"</code>; otherwise, it returns <code>"select-one"</code>.</dd>
<dt>{{domxref("HTMLSelectElement.validationMessage")}}{{ReadOnlyInline}}</dt>
<dd>A {{domxref("DOMString")}} representing a localized message that describes the validation constraints that the control does not satisfy (if any). This attribute is the empty string if the control is not a candidate for constraint validation (<code>willValidate</code> is false), or it satisfies its constraints.</dd>
<dt>{{domxref("HTMLSelectElement.validity")}}{{ReadOnlyInline}}</dt>
<dd>A {{domxref("ValidityState")}} reflecting the validity state that this control is in.</dd>
<dt>{{domxref("HTMLSelectElement.value")}}</dt>
<dd>A {{domxref("DOMString")}} reflecting the value of the form control (the first selected option).</dd>
<dt>{{domxref("HTMLSelectElement.willValidate")}}{{ReadOnlyInline}}</dt>
<dd>A {{jsxref("Boolean")}} that indicates whether the button is a candidate for constraint validation. It is false if any conditions bar it from constraint validation.</dd>
</dl>
<h2 id="Methods">Methods</h2>
<p><em>This interface inherits the methods of {{domxref("HTMLElement")}}, and of {{domxref("Element")}} and {{domxref("Node")}}.</em></p>
<dl>
<dt>{{domxref("HTMLSelectElement.add()")}}</dt>
<dd>Adds an element to the collection of <code>option</code> elements for this <code>select</code> element.</dd>
<dt>{{domxref("HTMLSelectElement.blur()")}}{{obsolete_inline}}</dt>
<dd>Removes input focus from this element. <em>This method is now implemented on {{domxref("HTMLElement")}}</em>.</dd>
<dt>{{domxref("HTMLSelectElement.checkValidity()")}}</dt>
<dd>Checks whether the element has any constraints and whether it satisfies them. If the element fails its constraints, the browser fires a cancelable {{event("invalid")}} event at the element (and returns <code>false</code>).</dd>
<dt>{{domxref("HTMLSelectElement.focus()")}}{{obsolete_inline}}</dt>
<dd>Gives input focus to this element. <em>This method is now implemented on {{domxref("HTMLElement")}}</em>.</dd>
<dt>{{domxref("HTMLSelectElement.item()")}}</dt>
<dd>Gets an item from the options collection for this {{HTMLElement("select")}} element. You can also access an item by specifying the index in array-style brackets or parentheses, without calling this method explicitly.</dd>
<dt>{{domxref("HTMLSelectElement.namedItem()")}}</dt>
<dd>Gets the item in the options collection with the specified name. The name string can match either the <code>id</code> or the <code>name</code> attribute of an option node. You can also access an item by specifying the name in array-style brackets or parentheses, without calling this method explicitly.</dd>
<dt>{{domxref("HTMLSelectElement.remove()")}}</dt>
<dd>Removes the element at the specified index from the options collection for this select element.</dd>
<dt>{{domxref("HTMLSelectElement.setCustomValidity()")}}</dt>
<dd>Sets the custom validity message for the selection element to the specified message. Use the empty string to indicate that the element does <em>not</em> have a custom validity error.</dd>
</dl>
<h2 id="範例">範例</h2>
<h3 id="Get_information_about_the_selected_option">Get information about the selected option</h3>
<pre class="brush: js">/* assuming we have the following HTML
<select id='s'>
<option>First</option>
<option selected>Second</option>
<option>Third</option>
</select>
*/
var select = document.getElementById('s');
// return the index of the selected option
console.log(select.selectedIndex); // 1
// return the value of the selected option
console.log(select.options[select.selectedIndex].value) // Second
</pre>
<p>A better way to track changes to the user's selection is to watch for the {{event("change")}} event to occur on the <code><select></code>. This will tell you when the value changes, and you can then update anything you need to. See <a href="/en-US/docs/Web/Events/change#Example_Change_event_on_a_select">the example provided</a> in the documentation for the <code>change</code> event for details.</p>
<h2 id="規範">規範</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td>{{SpecName('HTML WHATWG', '#htmlselectelement', 'HTMLSelectElement')}}</td>
<td>{{Spec2('HTML WHATWG')}}</td>
<td>Since the latest snapshot, {{SpecName('HTML5 W3C')}}, it adds the <code>autocomplete</code> property and the <code>reportValidity()</code> method.</td>
</tr>
<tr>
<td>{{SpecName('HTML5 W3C', 'forms.html#htmlselectelement', 'HTMLSelectElement')}}</td>
<td>{{Spec2('HTML5 W3C')}}</td>
<td>Is a snapshot of {{SpecName("HTML WHATWG")}}.<br>
It adds the <code>autofocus</code>, <code>form</code>, <code>required</code>, <code>labels</code>, <code>selectedOptions</code>, <code>willValidate</code>, <code>validity</code> and <code>validationMessage</code> properties.<br>
The <code>tabindex</code> property and the <code>blur()</code> and <code>focus()</code> methods have been moved to {{domxref("HTMLElement")}}.<br>
The methods <code>item()</code>, <code>namedItem()</code>, <code>checkValidity()</code> and <code>setCustomValidity()</code>.</td>
</tr>
<tr>
<td>{{SpecName('DOM2 HTML', 'html.html#ID-94282980', 'HTMLSelectElement')}}</td>
<td>{{Spec2('DOM2 HTML')}}</td>
<td><code>options</code> now returns an {{domxref("HTMLOptionsCollection")}}.<br>
<code>length</code> now returns an <code>unsigned long</code>.</td>
</tr>
<tr>
<td>{{SpecName('DOM1', 'level-one-html.html#ID-94282980', 'HTMLSelectElement')}}</td>
<td>{{Spec2('DOM1')}}</td>
<td>Initial definition</td>
</tr>
</tbody>
</table>
<h2 id="瀏覽器相容性">瀏覽器相容性</h2>
{{Compat("api.HTMLSelectElement")}}
<h2 id="參見">參見</h2>
<ul>
<li>The {{HTMLElement("select")}} HTML element, which implements this interface.</li>
</ul>
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