path: root/files/zh-cn/web/api/htmlselectelement/index.html

---
title: HTMLSelectElement
slug: Web/API/HTMLSelectElement
tags:
  - API
  - HTML DOM
  - HTMLSelectElement
  - Select
  - 参考
  - 接口
  - 选择
translation_of: Web/API/HTMLSelectElement
---
<div>
<p>{{APIRef("HTML DOM")}}</p>

<p><code><strong>HTMLSelectElement</strong></code> 接口表示一个 {{HTMLElement("select")}} HTML 元素。这个元素也通过 {{domxref("HTMLElement")}} 接口从其他 HTML 元素共享所有属性和方法。</p>

<p>{{InheritanceDiagram(600, 120)}}</p>
</div>

<h2 id="属性">属性</h2>

<p><em>这个接口从 {{domxref("HTMLElement")}}，{{domxref("Element")}} 和 {{domxref("Node")}} 继承属性。</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")}} ({{domxref("HTMLOptionElement")}}) 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 <code>true</code>, 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. Returns the <code>value</code> property of the first selected option element if there is one, otherwise the empty string.</dd>
 <dt>{{domxref("HTMLSelectElement.willValidate")}}{{ReadOnlyInline}}</dt>
 <dd>A {{jsxref("Boolean")}} that indicates whether the button is a candidate for constraint validation. It is <code>false</code> if any conditions bar it from constraint validation.</dd>
</dl>

<h2 id="方法">方法</h2>

<p><em>这个接口从 {{domxref("HTMLElement")}}，{{domxref("Element")}} 和 {{domxref("Node")}} 继承属性。</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 {{domxref("HTMLInputElement/invalid_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 <code>select</code> element.</dd>
 <dt>{{domxref("HTMLSelectElement.reportValidity()")}}</dt>
 <dd>This method reports the problems with the constraints on the element, if any, to the user. If there are problems, it fires a cancelable {{domxref("HTMLInputElement/invalid_event", "invalid")}} event at the element, and returns <code>false</code>; if there are no problems, it returns <code>true</code>.</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="事件">事件</h2>

<p>使用 {{domxref("EventTarget/addEventListener", "addEventListener()")}} 或给下面接口的 <code>on<em>eventname</em></code> 属性分配一个监听程序来监听这些事件：</p>

<dl>
 <dt>{{domxref("HTMLElement/input_event", "input")}} 事件</dt>
 <dd>当 {{HTMLElement("input")}}, {{HTMLElement("select")}}, 或 {{HTMLElement("textarea")}} 元素的 <code>value</code> 改变时触发该事件。</dd>
</dl>

<h2 id="示例">示例</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
&lt;select id='s'&gt;
    &lt;option&gt;First&lt;/option&gt;
    &lt;option selected&gt;Second&lt;/option&gt;
    &lt;option&gt;Third&lt;/option&gt;
&lt;/select&gt;
*/

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 {{domxref("HTMLElement/change_event", "change")}} event to occur on the <code>&lt;select&gt;</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/API/HTMLElement/change_event#&lt;select>_element">the example provided</a> in the documentation for the <code>change</code> event for details.</p>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">规范</th>
   <th scope="col">状态</th>
   <th scope="col">注释</th>
  </tr>
 </thead>
 <tbody>
  <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="浏览器兼容性">浏览器兼容性</h2>

<p>{{Compat("api.HTMLSelectElement")}}</p>

<h2 id="参见">参见</h2>

<ul>
 <li>{{HTMLElement("select")}} HTML 元素</li>
</ul>