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---
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:
<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>
<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>
<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">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) && typeof g !== 'undefined')
throw new TypeError('bad get');
d.get = g;
}
if (hasProperty(desc, 'set')) {
var s = desc.set;
if (!isCallable(s) && typeof s !== 'undefined')
throw new TypeError('bad set');
d.set = s;
}
if (('get' in d || 'set' in d) && ('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 < keys.length; i++)
descs.push([keys[i], convertToDescriptor(properties[keys[i]])]);
for (var i = 0; i < descs.length; i++)
Object.defineProperty(obj, descs[i][0], descs[i][1]);
return obj;
}
</pre>
<h2 id="規範">規範</h2>
{{Specifications}}
<h2 id="瀏覽器相容性">瀏覽器相容性</h2>
{{Compat}}
<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>
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