path: root/files/zh-tw/web/javascript/reference/global_objects/promise/all/index.html

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

<p><code><strong>Promise.all()</strong></code> 方法回傳一個 {{jsxref("Promise")}} 物件，當引數 <code>iterable</code> 中所有的 promises 都被實現（resolved），或引數 iterable 不含任何 promise 時，被實現。或以第一個被拒絕的 promise 的原因被拒絕。</p>

<h2 id="語法">語法</h2>

<pre class="syntaxbox"><var>Promise.all(iterable)</var>;</pre>

<dl>
 <dt>iterable</dt>
 <dd>一個 <a href="https://developer.mozilla.org/zh-TW/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterable_protocol">iterable</a> 物件像是 {{jsxref("Array")}} 或 {{jsxref("String")}}。</dd>
</dl>

<h3 id="回傳值">回傳值</h3>

<ul>
 <li>一個<strong>已被實現（already resolved）</strong>的 {{jsxref("Promise")}}，若傳入的 iterable 為空。</li>
 <li>一個<strong>非同步地被實現（asynchronously resolved）</strong>的 {{jsxref("Promise")}} 若傳入的 iterable 不含 promise。注意，Google Chrome 58 對此情形回傳一個<strong>已被解決</strong>的 promise。</li>
 <li>一個<strong>擱置（pending）</strong>的 {{jsxref("Promise")}}，對所有剩餘情形。此 promise 接著被<strong>非同步地</strong>被 resolved/rejected（只要堆疊為空）當 iterable 中所有的 promises 都被實現，或其中一個被拒絕。參見下方關於"Promise.all 的非同步與同步性質"的例子。</li>
</ul>

<h2 id="描述">描述</h2>

<p>此方法在聚集（aggregating）多個 promises 的結果時很有幫助。</p>

<p>實現（Fulfillment）：<br>
 若傳入空的 iterable，此方法（同步地）回傳一個已被解決的 promise。若所有傳入的 promises 都被實現，或都不是 promise，<code>Promise.all</code> 回傳的 promise 被非同步地實現。無論是哪個情形，回傳一個以 iterable 其內<strong>所有</strong>值（包含非 promise 值）作為引數的陣列被實現。<br>
  </p>

<p>拒絕（Rejection）：<br>
 若任一個傳入的 promise 被拒絕，Promise.all 非同步地以其值被拒絕，無論其他 promises 是否被解決。</p>

<h2 id="範例">範例</h2>

<h3 id="使用_Promise.all">使用 <code>Promise.all</code></h3>

<p><code>Promise.all</code> 等到全部實現（或一個拒絕）。</p>

<pre class="brush: js">var p1 = Promise.resolve(3);
var p2 = 1337;
var p3 = new Promise((resolve, reject) =&gt; {
  setTimeout(resolve, 100, 'foo');
});

Promise.all([p1, p2, p3]).then(values =&gt; {
  console.log(values); // [3, 1337, "foo"]
});</pre>

<p>若 iterable 含非 promise 值，它們將被忽略，但依然會被記入回傳 promise 陣列值（若被實現）：</p>

<pre class="brush: js">// this will be counted as if the iterable passed is empty, so it gets fulfilled
var p = Promise.all([1,2,3]);
// this will be counted as if the iterable passed contains only the resolved promise with value "444", so it gets fulfilled
var p2 = Promise.all([1,2,3, Promise.resolve(444)]);
// this will be counted as if the iterable passed contains only the rejected promise with value "555", so it gets rejected
var p3 = Promise.all([1,2,3, Promise.reject(555)]);

// using setTimeout we can execute code after the stack is empty
setTimeout(function(){
    console.log(p);
    console.log(p2);
    console.log(p3);
});

// logs
// Promise { &lt;state&gt;: "fulfilled", &lt;value&gt;: Array[3] }
// Promise { &lt;state&gt;: "fulfilled", &lt;value&gt;: Array[4] }
// Promise { &lt;state&gt;: "rejected", &lt;reason&gt;: 555 }</pre>

<h3 id="Promise.all_的非同步與同步性質"><code>Promise.all</code> 的非同步與同步性質</h3>

<p>以下例子驗證了 <code>Promise.all</code> 的非同步性質（asynchronicity）（或同步性質（synchronicity），若傳入的 iterable 是空的）：</p>

<pre class="brush: js">// we are passing as argument an array of promises that are already resolved,
// to trigger Promise.all as soon as possible
var resolvedPromisesArray = [Promise.resolve(33), Promise.resolve(44)];

var p = Promise.all(resolvedPromisesArray);
// immediately logging the value of p
console.log(p);

// using setTimeout we can execute code after the stack is empty
setTimeout(function(){
    console.log('the stack is now empty');
    console.log(p);
});

// logs, in order:
// Promise { &lt;state&gt;: "pending" }
// the stack is now empty
// Promise { &lt;state&gt;: "fulfilled", &lt;value&gt;: Array[2] }
</pre>

<p><code>當</code> <code>Promise.all</code> 被拒絕時發生一樣的事情：</p>

<pre class="brush: js">var mixedPromisesArray = [Promise.resolve(33), Promise.reject(44)];
var p = Promise.all(mixedPromisesArray);
console.log(p);
setTimeout(function(){
    console.log('the stack is now empty');
    console.log(p);
});

// logs
// Promise { &lt;state&gt;: "pending" }
// the stack is now empty
// Promise { &lt;state&gt;: "rejected", &lt;reason&gt;: 44 }
</pre>

<p>注意！<code>Promise.all</code> 同步地被解決<strong>若且唯若</strong>傳入的 iterable 為空：</p>

<pre class="brush: js">var p = Promise.all([]); // will be immediately resolved
var p2 = Promise.all([1337, "hi"]); // non-promise values will be ignored, but the evaluation will be done asynchronously
console.log(p);
console.log(p2)
setTimeout(function(){
    console.log('the stack is now empty');
    console.log(p2);
});

// logs
// Promise { &lt;state&gt;: "fulfilled", &lt;value&gt;: Array[0] }
// Promise { &lt;state&gt;: "pending" }
// the stack is now empty
// Promise { &lt;state&gt;: "fulfilled", &lt;value&gt;: Array[2] }
</pre>

<h3 id="Promise.all_的失敗優先（fail-fast）行為"><code>Promise.all</code> 的失敗優先（fail-fast）行為</h3>

<p><code>當任一個陣列成員被拒絕則</code> <code>Promise.all</code> 被拒絕。例如，若傳入四個將在一段時間後被解決的 promises，而其中一個立刻被拒絕，則 <code>Promise.all</code> 將立刻被拒絕。</p>

<pre class="brush: js">var p1 = new Promise((resolve, reject) =&gt; {
  setTimeout(resolve, 1000, 'one');
});
var p2 = new Promise((resolve, reject) =&gt; {
  setTimeout(resolve, 2000, 'two');
});
var p3 = new Promise((resolve, reject) =&gt; {
  setTimeout(resolve, 3000, 'three');
});
var p4 = new Promise((resolve, reject) =&gt; {
  setTimeout(resolve, 4000, 'four');
});
var p5 = new Promise((resolve, reject) =&gt; {
  reject('reject');
});

Promise.all([p1, p2, p3, p4, p5]).then(values =&gt; {
  console.log(values);
}, reason =&gt; {
  console.log(reason)
});

//From console:
//"reject"

//You can also use .catch
Promise.all([p1, p2, p3, p4, p5]).then(values =&gt; {
  console.log(values);
}).catch(reason =&gt; {
  console.log(reason)
});

//From console:
//"reject"

</pre>

<h2 id="規範">規範</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-promise.all', 'Promise.all')}}</td>
   <td>{{Spec2('ES2015')}}</td>
   <td>Initial definition in an ECMA standard.</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-promise.all', 'Promise.all')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="瀏覽器相容性">瀏覽器相容性</h2>

<p class="hidden">To contribute to this compatibility data, please write a pull request against this repository: <a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a>.</p>

<p>{{Compat("javascript.builtins.Promise.all")}}</p>

<h2 id="參見">參見</h2>

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