--- 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) > -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 && 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>