path: root/files/zh-cn/web/javascript/enumerability_and_ownership_of_properties/index.html

---
title: 属性的可枚举性和所有权
slug: Web/JavaScript/Enumerability_and_ownership_of_properties
tags:
  - JavaScript
  - 对象
  - 属性
translation_of: Web/JavaScript/Enumerability_and_ownership_of_properties
---
<div>{{JsSidebar("More")}}</div>

<p>可枚举属性是指那些内部 “可枚举” 标志设置为 <code>true</code> 的属性，对于通过直接的赋值和属性初始化的属性，该标识值默认为即为 <code>true</code>，对于通过 <a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty">Object.defineProperty</a> 等定义的属性，该标识值默认为 <code>false</code>。可枚举的属性可以通过 <a href="/zh-CN/docs/Web/JavaScript/Reference/Statements/for...in">for...in</a> 循环进行遍历（除非该属性名是一个 <a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Symbol">Symbol</a>）。属性的所有权是通过判断该属性是否直接属于某个对象决定的，而不是通过原型链继承的。一个对象的所有的属性可以一次性的获取到。有一些内置的方法可以用于判断、迭代/枚举以及获取对象的一个或一组属性，下表对这些方法进行了列举。对于部分不可用的类别，下方的示例代码对获取方法进行了演示。</p>

<div>
<table>
 <caption>属性的可枚举性和所有权 - 内置的判断、访问和迭代方法</caption>
 <tbody>
  <tr>
   <th>作用</th>
   <th>自身对象</th>
   <th>自身对象及其原型链</th>
   <th>仅原型链</th>
  </tr>
  <tr>
   <td>判断</td>
   <td>
    <table>
     <thead>
      <tr>
       <th scope="col">可枚举属性</th>
       <th scope="col">不可枚举属性</th>
       <th scope="col">可枚举属性及不可枚举属性</th>
      </tr>
     </thead>
     <tbody>
      <tr>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable">propertyIsEnumerable</a></code><br>
        <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty">hasOwnProperty</a></code></td>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty">hasOwnProperty</a></code> 获取属性后使用 <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable">propertyIsEnumerable</a></code> 过滤可枚举属性</td>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty">hasOwnProperty</a></code></td>
      </tr>
     </tbody>
    </table>
   </td>
   <td>
    <table>
     <thead>
      <tr>
       <th scope="col">可枚举属性</th>
       <th scope="col">不可枚举属性</th>
       <th scope="col">可枚举属性及不可枚举属性</th>
      </tr>
     </thead>
     <tbody>
      <tr>
       <td>需要额外代码实现</td>
       <td>需要额外代码实现</td>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Operators/in">in</a></code></td>
      </tr>
     </tbody>
    </table>
   </td>
   <td>需要额外代码实现</td>
  </tr>
  <tr>
   <td>访问</td>
   <td>
    <table>
     <thead>
      <tr>
       <th scope="col">可枚举属性</th>
       <th scope="col">不可枚举属性</th>
       <th scope="col">可枚举属性及不可枚举属性</th>
      </tr>
     </thead>
     <tbody>
      <tr>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/keys">Object.keys</a></code><br>
        <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code><br>
        <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code></td>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code>、<code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a> </code>获取属性后使用 <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable">propertyIsEnumerable</a></code> 过滤可枚举属性</td>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code><br>
        <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code></td>
      </tr>
     </tbody>
    </table>
   </td>
   <td>需要额外代码实现</td>
   <td>需要额外代码实现</td>
  </tr>
  <tr>
   <td>迭代</td>
   <td>
    <table>
     <thead>
      <tr>
       <th scope="col">可枚举属性</th>
       <th scope="col">不可枚举属性</th>
       <th scope="col">可枚举属性及不可枚举属性</th>
      </tr>
     </thead>
     <tbody>
      <tr>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/keys">Object.keys</a></code><br>
        <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code><br>
        <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code></td>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code>、<code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code> 获取属性后使用 <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable">propertyIsEnumerable</a></code> 过滤可枚举属性</td>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames">getOwnPropertyNames</a></code><br>
        <code><a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols">getOwnPropertySymbols</a></code></td>
      </tr>
     </tbody>
    </table>
   </td>
   <td>
    <table>
     <thead>
      <tr>
       <th scope="col">可枚举属性</th>
       <th scope="col">不可枚举属性</th>
       <th scope="col">可枚举属性及不可枚举属性</th>
      </tr>
     </thead>
     <tbody>
      <tr>
       <td><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Statements/for...in">for..in</a></code><br>
        （同时会排除 Symbol）</td>
       <td>需要额外代码实现</td>
       <td>需要额外代码实现</td>
      </tr>
     </tbody>
    </table>
   </td>
   <td>需要额外代码实现</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="通过可枚举性和所有权获取对象的属性">通过可枚举性和所有权获取对象的属性</h2>

<p>注：以下实现并非使用于所有情况的最优算法，但可以快捷的展示语言特性。</p>

<ul>
 <li>使用 <code>SimplePropertyRetriever.theGetMethodYouWant(obj).indexOf(prop) &gt; -1</code> 时将发生判断操作。</li>
 <li>使用 <code>SimplePropertyRetriever.theGetMethodYouWant(obj).forEach(function (value, prop) {});</code> 时将发生迭代操作。 (或使用 <code>filter()</code>、<code>map()</code> 等方法)</li>
</ul>

<pre class="brush: js">var SimplePropertyRetriever = {
    getOwnEnumerables: function(obj) {
        return this._getPropertyNames(obj, true, false, this._enumerable);
         // Or could use for..in filtered with hasOwnProperty or just this: return Object.keys(obj);
    },
    getOwnNonenumerables: function(obj) {
        return this._getPropertyNames(obj, true, false, this._notEnumerable);
    },
    getOwnEnumerablesAndNonenumerables: function(obj) {
        return this._getPropertyNames(obj, true, false, this._enumerableAndNotEnumerable);
        // Or just use: return Object.getOwnPropertyNames(obj);
    },
    getPrototypeEnumerables: function(obj) {
        return this._getPropertyNames(obj, false, true, this._enumerable);
    },
    getPrototypeNonenumerables: function(obj) {
        return this._getPropertyNames(obj, false, true, this._notEnumerable);
    },
    getPrototypeEnumerablesAndNonenumerables: function(obj) {
        return this._getPropertyNames(obj, false, true, this._enumerableAndNotEnumerable);
    },
    getOwnAndPrototypeEnumerables: function(obj) {
        return this._getPropertyNames(obj, true, true, this._enumerable);
        // Or could use unfiltered for..in
    },
    getOwnAndPrototypeNonenumerables: function(obj) {
        return this._getPropertyNames(obj, true, true, this._notEnumerable);
    },
    getOwnAndPrototypeEnumerablesAndNonenumerables: function(obj) {
        return this._getPropertyNames(obj, true, true, this._enumerableAndNotEnumerable);
    },
    // Private static property checker callbacks
    _enumerable: function(obj, prop) {
        return obj.propertyIsEnumerable(prop);
    },
    _notEnumerable: function(obj, prop) {
        return !obj.propertyIsEnumerable(prop);
    },
    _enumerableAndNotEnumerable: function(obj, prop) {
        return true;
    },
    // Inspired by http://stackoverflow.com/a/8024294/271577
    _getPropertyNames: function getAllPropertyNames(obj, iterateSelfBool, iteratePrototypeBool, includePropCb) {
        var props = [];

        do {
            if (iterateSelfBool) {
                Object.getOwnPropertyNames(obj).forEach(function(prop) {
                    if (props.indexOf(prop) === -1 &amp;&amp; includePropCb(obj, prop)) {
                        props.push(prop);
                    }
                });
            }
            if (!iteratePrototypeBool) {
                break;
            }
            iterateSelfBool = true;
        } while (obj = Object.getPrototypeOf(obj));

        return props;
    }
};</pre>

<h2 id="统计表">统计表</h2>

<div>
<table>
 <thead>
  <tr>
   <th scope="row"></th>
   <th scope="col"><code>in</code></th>
   <th scope="col"><code>for..in</code></th>
   <th scope="col"><code>obj.hasOwnProperty</code></th>
   <th scope="col"><code>obj.propertyIsEnumerable</code></th>
   <th scope="col"><code>Object.keys</code></th>
   <th scope="col"><code>Object.getOwnPropertyNames</code></th>
   <th scope="col"><code>Object.getOwnPropertyDescriptors</code></th>
   <th scope="col"><code>Reflect.ownKeys()</code></th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <th scope="row">自身的可枚举属性</th>
   <td>true</td>
   <td>true</td>
   <td>true</td>
   <td>true</td>
   <td>true</td>
   <td>true</td>
   <td>true</td>
   <td>true</td>
  </tr>
  <tr>
   <th scope="row">自身的不可枚举属性</th>
   <td>true</td>
   <td>false</td>
   <td>true</td>
   <td>false</td>
   <td>false</td>
   <td>true</td>
   <td>true</td>
   <td>true</td>
  </tr>
  <tr>
   <th scope="row">自身的Symbol 键</th>
   <td>true</td>
   <td>false</td>
   <td>true</td>
   <td>true</td>
   <td>false</td>
   <td>false</td>
   <td>true</td>
   <td>true</td>
  </tr>
  <tr>
   <th scope="row">继承的可枚举属性</th>
   <td>true</td>
   <td>true</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
  </tr>
  <tr>
   <th scope="row">继承的不可枚举属性</th>
   <td>true</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
  </tr>
  <tr>
   <th scope="row">继承的 Symbol 键</th>
   <td>true</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
   <td>false</td>
  </tr>
 </tbody>
</table>
</div>

<h2 id="参见">参见</h2>

<ul>
 <li><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Operators/in">in</a></code></li>
 <li><code><a href="/zh-CN/docs/Web/JavaScript/Reference/Statements/for...in">for..in</a></code></li>
 <li>{{jsxref("Object.hasOwnProperty()")}}</li>
 <li>{{jsxref("Object.propertyIsEnumerable()")}}</li>
 <li>{{jsxref("Object.getOwnPropertyNames()")}}</li>
 <li>{{jsxref("Object.keys()")}}</li>
 <li>{{jsxref("Object.getOwnPropertyDescriptors()")}}</li>
</ul>