---
title: Promise.prototype.catch()
slug: Web/JavaScript/Reference/Global_Objects/Promise/catch
tags:
  - Promise
  - Promise.prototype.catch()
translation_of: Web/JavaScript/Reference/Global_Objects/Promise/catch
---
<div>{{JSRef}}</div>

<p><strong>catch()</strong> 方法返回一个<a href="/zh-CN/docs/Web/API/Promise">Promise</a>，并且处理拒绝的情况。它的行为与调用{{jsxref("Promise.then", "Promise.prototype.then(undefined, onRejected)")}} 相同。 (事实上, calling <code>obj.catch(onRejected)</code> 内部calls <code>obj.then(undefined, onRejected)</code>).</p>

<h2 id="Syntax">语法</h2>

<pre class="syntaxbox"><var>p.catch(onRejected)</var>;

p.catch(function(reason) {
   // 拒绝
});
</pre>

<h3 id="参数">参数</h3>

<dl>
 <dt><strong>onRejected</strong></dt>
 <dd>当Promise 被rejected时,被调用的一个{{jsxref("Function")}}。 该函数拥有一个参数：<code>reason</code>    rejection 的原因。如果 <code>onRejected</code> 抛出一个错误或返回一个本身失败的 Promise ，  通过 <code>catch()</code> 返回的Promise 被rejected；否则，它将显示为成功（resolved）。</dd>
</dl>

<h3 id="返回值">返回值</h3>

<p>一个{{jsxref("Promise")}}.</p>

<h2 id="Description">描述</h2>

<p><code>catch </code>方法可以用于您的promise组合中的错误处理。</p>

<p>Internally calls <code>Promise.prototype.then</code> on the object upon which is called, passing the parameters <code>undefined</code> and the <code>onRejected</code> handler received; then returns the value of that call (which is a {{jsxref("Promise")}}).</p>

<h2 id="示例">示例</h2>

<h3 id="使用链式语句的_catch方法">使用链式语句的 <code>catch</code>方法</h3>

<pre class="brush: js"><code>var p1 = new Promise(function(resolve, reject) {
  resolve('Success');
});</code>

p1.then(function(value) {
  console.log(value); // "Success!"
  throw 'oh, no!';
}).catch(function(e) {
  console.log(e); // "oh, no!"
}).then(function(){
  console.log('after a catch the chain is restored');
}, function () {
  console.log('Not fired due to the catch');
});

// 以下行为与上述相同
p1.then(function(value) {
  console.log(value); // "Success!"
  return Promise.reject('oh, no!');
}).catch(function(e) {
  console.log(e); // "oh, no!"
}).then(function(){
  console.log('after a catch the chain is restored');
}, function () {
  console.log('Not fired due to the catch');
});</pre>

<h3 id="捕获抛出的错误">捕获抛出的错误</h3>

<pre class="brush: js"><code>// 抛出一个错误，大多数时候将调用catch方法
var p1 = new Promise(function(resolve, reject) {
  throw 'Uh-oh!';
});

p1.catch(function(e) {
  console.log(e); // "Uh-oh!"
});

// 在异步函数中抛出的错误不会被catch捕获到
var p2 = new Promise(function(resolve, reject) {
  setTimeout(function() {
    throw 'Uncaught Exception!';
  }, 1000);
});

p2.catch(function(e) {
  console.log(e); // 不会执行
});

// 在resolve()后面抛出的错误会被忽略
var p3 = new Promise(function(resolve, reject) {
  resolve();
  throw 'Silenced Exception!';
});

p3.catch(function(e) {
   console.log(e); // 不会执行
});</code></pre>

<h3 id="如果已决议">如果已决议</h3>

<pre><code>//创建一个新的 Promise ，且已决议
var p1 = Promise.resolve("calling next");

var p2 = p1.catch(function (reason) {
    //这个方法永远不会调用
    console.log("catch p1!");
    console.log(reason);
});

p2.then(function (value) {
    console.log("next promise's onFulfilled"); /* next promise's onFulfilled */
    console.log(value); /* calling next */
}, function (reason) {
    console.log("next promise's onRejected");
    console.log(reason);
});</code></pre>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">规范</th>
   <th scope="col">状态</th>
   <th scope="col">备注</th>
  </tr>
  <tr>
   <td><a href="https://github.com/domenic/promises-unwrapping">domenic/promises-unwrapping</a></td>
   <td>{{Spec2('ES6')}}</td>
   <td>Initial definition in an ECMA standard.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-promise.prototype.catch', 'Promise.prototype.catch')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<p>{{Compat("javascript/promise","Promise.prototype.catch")}}</p>

<h2 id="相关链接">相关链接</h2>

<ul>
 <li>{{jsxref("Promise")}}</li>
 <li>{{jsxref("Promise.prototype.then()")}}</li>
</ul>