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---
title: FetchEvent.respondWith()
slug: Web/API/FetchEvent/respondWith
translation_of: Web/API/FetchEvent/respondWith
---
<p>{{APIRef("Service Workers API")}}{{SeeCompatTable}}</p>
<p>{{domxref("FetchEvent")}} 接口的 <strong><code>respondWith()</code></strong> 方法旨在包裹代码，这些代码为来自受控页面的request生成自定义的response。这些代码通过返回一个 {{domxref("Response")}} 、 <a class="external external-icon" href="http://fetch.spec.whatwg.org/#concept-network-error">network error</a> 或者 <code><a class="external external-icon" href="http://fetch.spec.whatwg.org/#concept-fetch">Fetch</a>的方式</code>resolve。</p>
<p>有关跨域内容污染的渲染端安全检测与 {{domxref("Response")}} 体的透明度（或者不透明度）相关联，而不是URL。如果request是一个顶级的导航，而返回值是一个类型属性不透明的 {{domxref("Response")}}（即不透明响应体），一个 <a class="external external-icon" href="http://fetch.spec.whatwg.org/#concept-network-error">network error</a> 将被返回给 <code><a class="external external-icon" href="http://fetch.spec.whatwg.org/#concept-fetch">Fetch</a>。所有成功（非网络错误）响</code>应的最终URL是请求的URL。</p>
<h2 id="语法">语法</h2>
<pre class="brush: js">FetchEvent.respondWith(
//Promise that resolves to a Response or a network error.
)</pre>
<h3 id="返回值">返回值</h3>
<p>Void.</p>
<h3 id="参数">参数</h3>
<p>任何自定义的响应生成代码。</p>
<h2 id="示例">示例</h2>
<p>该代码片段来自 <a href="https://github.com/GoogleChrome/samples/blob/gh-pages/service-worker/prefetch/service-worker.js">service worker fetch sample</a> (<a class="external external-icon" href="https://googlechrome.github.io/samples/service-worker/prefetch/">run the fetch sample live</a>)。 {{domxref("ServiceWorkerGlobalScope.onfetch")}} 事件处理程序侦听 {{event("fetch")}} 事件。当触发时，{{domxref("FetchEvent.respondWith", "FetchEvent.respondWith(any value)")}} 返回一个promise给受控页面。该promise在 {{domxref("Cache")}} 对象中查询第一个匹配URL请求。如果没有发现匹配项，该代码将转而从网络获取响应。</p>
<p>该代码也处理从 {{domxref("ServiceWorkerGlobalScope.fetch")}} 操作中抛出的异常。请注意，HTTP错误响应（例如404）不会触发异常。 它将返回具有相应错误代码集的正常响应对象。</p>
<pre class="brush: js">self.addEventListener('fetch', function(event) {
console.log('Handling fetch event for', event.request.url);
event.respondWith(
caches.match(event.request).then(function(response) {
if (response) {
console.log('Found response in cache:', response);
return response;
}
console.log('No response found in cache. About to fetch from network...');
return fetch(event.request).then(function(response) {
console.log('Response from network is:', response);
return response;
}).catch(function(error) {
console.error('Fetching failed:', error);
throw error;
});
})
);
});</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('Service Workers', '#fetch-event-respondwith-method', 'respondWith()')}}</td>
<td>{{Spec2('Service Workers')}}</td>
<td>Initial definition.</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
{{Compat("api.FetchEvent.respondWith")}}
<h2 id="请参见">请参见</h2>
<ul>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorker_API/Using_Service_Workers">Using Service Workers</a></li>
<li><a class="external external-icon" href="https://github.com/mdn/sw-test">Service workers basic code example</a></li>
<li><a class="external external-icon" href="https://jakearchibald.github.io/isserviceworkerready/">Is ServiceWorker ready?</a></li>
<li>{{jsxref("Promise")}}</li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/Guide/Performance/Using_web_workers">Using web workers</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API">Fetch API</a></li>
</ul>
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