From 33058f2b292b3a581333bdfb21b8f671898c5060 Mon Sep 17 00:00:00 2001
From: Peter Bengtsson <mail@peterbe.com>
Date: Tue, 8 Dec 2020 14:40:17 -0500
Subject: initial commit

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+---
+title: handler.get()
+slug: Web/JavaScript/Reference/Global_Objects/Proxy/handler/get
+tags:
+  - ECMAScript6
+  - JavaScript
+  - Method
+  - Proxy
+translation_of: Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/get
+---
+<div>{{JSRef}}</div>
+
+<p><strong><code>handler.get()</code></strong> 方法用于拦截对象的读取属性操作。</p>
+
+<h2 id="语法">语法</h2>
+
+<pre class="brush: js">var p = new Proxy(target, {
+  get: function(target, property, receiver) {
+  }
+});
+</pre>
+
+<h3 id="参数">参数</h3>
+
+<p>以下是传递给get方法的参数，<code>this上下文绑定在</code>handler对象上.</p>
+
+<dl>
+ <dt><code>target</code></dt>
+ <dd>目标对象。</dd>
+ <dt><code>property</code></dt>
+ <dd>被获取的属性名。</dd>
+ <dt><code>receiver</code></dt>
+ <dd>Proxy或者继承Proxy的对象</dd>
+</dl>
+
+<h3 id="返回值">返回值</h3>
+
+<p>get方法可以返回任何值。</p>
+
+<h2 id="描述">描述</h2>
+
+<p><strong><code>handler.get</code></strong> 方法用于拦截对象的读取属性操作。</p>
+
+<h3 id="拦截">拦截</h3>
+
+<p>该方法会拦截目标对象的以下操作:</p>
+
+<ul>
+ <li>访问属性: <code>proxy[foo]和</code> <code>proxy.bar</code></li>
+ <li>访问原型链上的属性: <code>Object.create(proxy)[foo]</code></li>
+ <li>{{jsxref("Reflect.get()")}}</li>
+</ul>
+
+<h3 id="约束">约束</h3>
+
+<p>如果违背了以下的约束，proxy会抛出 {{jsxref("TypeError")}}:</p>
+
+<ul>
+ <li>如果要访问的目标属性是不可写以及不可配置的，则返回的值必须与该目标属性的值相同。</li>
+ <li>如果要访问的目标属性没有配置访问方法，即get方法是undefined的，则返回值必须为undefined。</li>
+</ul>
+
+<h2 id="示例">示例</h2>
+
+<p>以下代码演示如何拦截属性值的读取操作。</p>
+
+<pre class="brush: js">var p = new Proxy({}, {
+  get: function(target, prop, receiver) {
+    console.log("called: " + prop);
+    return 10;
+  }
+});
+
+console.log(p.a); // "called: a"
+                  // 10
+</pre>
+
+<p>以下代码演示违反约束的情况。</p>
+
+<pre class="brush: js">var obj = {};
+Object.defineProperty(obj, "a", {
+  configurable: false,
+  enumerable: false,
+  value: 10,
+  writable: false
+});
+
+var p = new Proxy(obj, {
+  get: function(target, prop) {
+    return 20;
+  }
+});
+
+p.a; //会抛出TypeError
+</pre>
+
+<h2 id="规范">规范</h2>
+
+<table class="standard-table">
+ <tbody>
+  <tr>
+   <th scope="col">Specification</th>
+   <th scope="col">Status</th>
+   <th scope="col">Comment</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('ES2015', '#sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver', '[[Get]]')}}</td>
+   <td>{{Spec2('ES2015')}}</td>
+   <td>Initial definition.</td>
+  </tr>
+  <tr>
+   <td>{{SpecName('ESDraft', '#sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver', '[[Get]]')}}</td>
+   <td>{{Spec2('ESDraft')}}</td>
+   <td> </td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="浏览器兼容性">浏览器兼容性</h2>
+
+<div>{{CompatibilityTable}}</div>
+
+<div id="compat-desktop">
+<table class="compat-table">
+ <tbody>
+  <tr>
+   <th>Feature</th>
+   <th>Chrome</th>
+   <th>Firefox (Gecko)</th>
+   <th>Internet Explorer</th>
+   <th>Opera</th>
+   <th>Safari</th>
+  </tr>
+  <tr>
+   <td>Basic support</td>
+   <td>{{CompatUnknown}}</td>
+   <td>{{CompatGeckoDesktop("18")}}</td>
+   <td>{{CompatUnknown}}</td>
+   <td>{{CompatUnknown}}</td>
+   <td>{{CompatUnknown}}</td>
+  </tr>
+ </tbody>
+</table>
+</div>
+
+<div id="compat-mobile">
+<table class="compat-table">
+ <tbody>
+  <tr>
+   <th>Feature</th>
+   <th>Android</th>
+   <th>Chrome for Android</th>
+   <th>Firefox Mobile (Gecko)</th>
+   <th>IE Mobile</th>
+   <th>Opera Mobile</th>
+   <th>Safari Mobile</th>
+  </tr>
+  <tr>
+   <td>Basic support</td>
+   <td>{{CompatUnknown}}</td>
+   <td>{{CompatUnknown}}</td>
+   <td>{{CompatGeckoMobile("18")}}</td>
+   <td>{{CompatUnknown}}</td>
+   <td>{{CompatUnknown}}</td>
+   <td>{{CompatUnknown}}</td>
+  </tr>
+ </tbody>
+</table>
+</div>
+
+<h2 id="另见">另见</h2>
+
+<ul>
+ <li>{{jsxref("Proxy")}}</li>
+ <li>{{jsxref("Proxy.handler", "handler")}}</li>
+ <li>{{jsxref("Reflect.get()")}}</li>
+</ul>
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