path: root/files/zh-tw/web/javascript/reference/global_objects/object/defineproperties/index.html

---
title: Object.defineProperties()
slug: Web/JavaScript/Reference/Global_Objects/Object/defineProperties
translation_of: Web/JavaScript/Reference/Global_Objects/Object/defineProperties
---
<div>{{JSRef}}</div>

<p><code><strong>Object.defineProperties()</strong></code> 函式可定義新的或是修改已存在的物件屬性，並回傳修改後的物件。</p>

<h2 id="語法">語法</h2>

<pre class="syntaxbox"><code>Object.defineProperties(<var>obj</var>, <var>props</var>)</code></pre>

<h3 id="參數">參數</h3>

<dl>
 <dt><code>obj</code></dt>
 <dd>The object on which to define or modify properties.</dd>
 <dt><code>props</code></dt>
 <dd>An object whose own enumerable properties constitute descriptors for the properties to be defined or modified. Property descriptors present in objects come in two main flavors: data descriptors and accessor descriptors (see {{jsxref("Object.defineProperty()")}} for more details). Descriptors have the following keys:</dd>
 <dd>
 <dl>
  <dt><code>configurable</code></dt>
  <dd><code>true</code> if and only if the type of this property descriptor may be changed and if the property may be deleted from the corresponding object.<br>
  <strong>預設為 <code>false</code>.</strong></dd>
  <dt><code>enumerable</code></dt>
  <dd><code>若該屬性設為 true，則該屬性可被物件所列舉。</code><br>
  <strong>預設為 <code>false</code>.</strong></dd>
 </dl>

 <dl>
  <dt><code>value</code></dt>
  <dd>The value associated with the property. Can be any valid JavaScript value (number, object, function, etc).<br>
  <strong>預設為 {{jsxref("undefined")}}.</strong></dd>
  <dt><code>writable</code></dt>
  <dd><code>若該屬性為 true</code>，則該屬性可透過{{jsxref("Operators/Assignment_Operators", "賦予運算子", "", 1)}}所改變<br>
  <strong>預設為 <code>false</code>.</strong></dd>
 </dl>

 <dl>
  <dt><code>get</code></dt>
  <dd>A function which serves as a getter for the property, or {{jsxref("undefined")}} if there is no getter. The function return will be used as the value of property.<br>
  <strong>預設為 {{jsxref("undefined")}}.</strong></dd>
  <dt><code>set</code></dt>
  <dd>A function which serves as a setter for the property, or {{jsxref("undefined")}} if there is no setter. The function will receive as only argument the new value being assigned to the property.<br>
  <strong>預設為 {{jsxref("undefined")}}.</strong></dd>
 </dl>
 </dd>
</dl>

<h3 id="回傳值">回傳值</h3>

<p>The object that was passed to the function.</p>

<h2 id="描述">描述</h2>

<p><code>Object.defineProperties</code>, in essence, defines all properties corresponding to the enumerable own properties of <code>props</code> on the object <code>obj</code> object.</p>

<h2 id="範例">範例</h2>

<pre class="brush: js">var obj = {};
Object.defineProperties(obj, {
  'property1': {
    value: true,
    writable: true
  },
  'property2': {
    value: 'Hello',
    writable: false
  }
  // etc. etc.
});
</pre>

<h2 id="Polyfill">Polyfill</h2>

<p>Assuming a pristine execution environment with all names and properties referring to their initial values, <code>Object.defineProperties</code> is almost completely equivalent (note the comment in <code>isCallable</code>) to the following reimplementation in JavaScript:</p>

<pre class="brush: js;highlight:[8]">function defineProperties(obj, properties) {
  function convertToDescriptor(desc) {
    function hasProperty(obj, prop) {
      return Object.prototype.hasOwnProperty.call(obj, prop);
    }

    function isCallable(v) {
      // NB: modify as necessary if other values than functions are callable.
      return typeof v === 'function';
    }

    if (typeof desc !== 'object' || desc === null)
      throw new TypeError('bad desc');

    var d = {};

    if (hasProperty(desc, 'enumerable'))
      d.enumerable = !!desc.enumerable;
    if (hasProperty(desc, 'configurable'))
      d.configurable = !!desc.configurable;
    if (hasProperty(desc, 'value'))
      d.value = desc.value;
    if (hasProperty(desc, 'writable'))
      d.writable = !!desc.writable;
    if (hasProperty(desc, 'get')) {
      var g = desc.get;

      if (!isCallable(g) &amp;&amp; typeof g !== 'undefined')
        throw new TypeError('bad get');
      d.get = g;
    }
    if (hasProperty(desc, 'set')) {
      var s = desc.set;
      if (!isCallable(s) &amp;&amp; typeof s !== 'undefined')
        throw new TypeError('bad set');
      d.set = s;
    }

    if (('get' in d || 'set' in d) &amp;&amp; ('value' in d || 'writable' in d))
      throw new TypeError('identity-confused descriptor');

    return d;
  }

  if (typeof obj !== 'object' || obj === null)
    throw new TypeError('bad obj');

  properties = Object(properties);

  var keys = Object.keys(properties);
  var descs = [];

  for (var i = 0; i &lt; keys.length; i++)
    descs.push([keys[i], convertToDescriptor(properties[keys[i]])]);

  for (var i = 0; i &lt; descs.length; i++)
    Object.defineProperty(obj, descs[i][0], descs[i][1]);

  return obj;
}
</pre>

<h2 id="規格">規格</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">註記</th>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-15.2.3.7', 'Object.defineProperties')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td>Initial definition. Implemented in JavaScript 1.8.5</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-object.defineproperties', 'Object.defineProperties')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td> </td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-object.defineproperties', 'Object.defineProperties')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="瀏覽器相容性">瀏覽器相容性</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Firefox (Gecko)</th>
   <th>Chrome</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatGeckoDesktop("2")}}</td>
   <td>{{CompatChrome("5")}}</td>
   <td>{{CompatIE("9")}}</td>
   <td>{{CompatOpera("11.60")}}</td>
   <td>{{CompatSafari("5")}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>Android</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatGeckoMobile("2")}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatOperaMobile("11.5")}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="參閱">參閱</h2>

<ul>
 <li>{{jsxref("Object.defineProperty()")}}</li>
 <li>{{jsxref("Object.keys()")}}</li>
 <li><a href="/en-US/docs/Enumerability_and_ownership_of_properties">Enumerability and ownership of properties</a></li>
</ul>