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+---
+title: Request.cache
+slug: Web/API/Request/cache
+translation_of: Web/API/Request/cache
+---
+<div>{{APIRef("Fetch")}}</div>
+
+<p><strong><code>cache</code></strong> 作为{{domxref("Request")}} 接口只读属性包含着请求的缓存模式。它控制着请求以何种方式与浏览器的  <a href="/en-US/docs/Web/HTTP/Caching">HTTP </a>缓存进行交互。</p>
+
+<h2 id="Syntax">Syntax</h2>
+
+<pre class="brush: js">var currentCacheMode = request.cache;</pre>
+
+<h3 id="Value">Value</h3>
+
+<p>A <code>RequestCache</code> value. The available values are:</p>
+
+<ul>
+ <li><code>default</code> — 浏览器从HTTP缓存中寻找匹配的请求。
+
+ <ul>
+ <li>如果缓存匹配上并且有效( <a href="/en-US/docs/Web/HTTP/Caching#Freshness">fresh</a>), 它将直接从缓存中返回资源。</li>
+ <li>如果缓存匹配上但已经过期 ,浏览器将会使用传统( <a href="/en-US/docs/Web/HTTP/Conditional_requests">conditional request</a> )的请求方式去访问远程服务器 。如果服务器端显示资源没有改动,它将从缓存中返回资源。否则,如果服务器显示资源变动,那么重新从服务器下载资源更新缓存。</li>
+ <li>如果缓存没有匹配,浏览器将会以普通方式请求,并且更新已经下载的资源缓存。</li>
+ </ul>
+ </li>
+ <li><code>no-store</code> — 浏览器直接从远程服务器获取资源,不查看缓存,并且不会使用下载的资源更新缓存。</li>
+ <li><code>reload</code> — 浏览器直接从远程服务器获取资源,不查看缓存,然后使用下载的资源更新缓存。</li>
+ <li><code>no-cache</code> — 浏览器在其HTTP缓存中寻找匹配的请求。
+ <ul>
+ <li>如果有匹配,无论是新的还是陈旧的,浏览器都会向远程服务器发出条件请求。如果服务器指示资源没有更改,则将从缓存中返回该资源。否则,将从服务器下载资源并更新缓存。</li>
+ <li>如果没有匹配,浏览器将发出正常请求,并使用下载的资源更新缓存。</li>
+ </ul>
+ <code>force-cache </code>— 浏览器在其HTTP缓存中寻找匹配的请求。
+
+ <ul>
+ <li>如果有匹配项,不管是新匹配项还是旧匹配项,都将从缓存中返回。</li>
+ <li>如果没有匹配,浏览器将发出正常请求,并使用下载的资源更新缓存。</li>
+ </ul>
+ </li>
+ <li><code>only-if-cached</code> — 浏览器在其HTTP缓存中寻找匹配的请求。
+ <ul>
+ <li>如果有匹配项(新的或旧的),则从缓存中返回。</li>
+ <li>如果没有匹配,浏览器将返回一个错误。</li>
+ </ul>
+ The <code>"only-if-cached"</code> mode can only be used if the request's <code><a href="https://developer.mozilla.org/en-US/docs/Web/API/Request/mode">mode</a></code> is <code>"same-origin"</code>. Cached redirects will be followed if the request's <code>redirect</code> property is <code>"follow"</code> and the redirects do not violate the <code>"same-origin"</code> mode.</li>
+</ul>
+
+<h2 id="Example">Example</h2>
+
+<pre class="brush: js">// Download a resource with cache busting, to bypass the cache
+// completely.
+fetch("some.json", {cache: "no-store"})
+ .then(function(response) { /* consume the response */ });
+
+// Download a resource with cache busting, but update the HTTP
+// cache with the downloaded resource.
+fetch("some.json", {cache: "reload"})
+ .then(function(response) { /* consume the response */ });
+
+// Download a resource with cache busting when dealing with a
+// properly configured server that will send the correct ETag
+// and Date headers and properly handle If-Modified-Since and
+// If-None-Match request headers, therefore we can rely on the
+// validation to guarantee a fresh response.
+fetch("some.json", {cache: "no-cache"})
+ .then(function(response) { /* consume the response */ });
+
+// Download a resource with economics in mind! Prefer a cached
+// albeit stale response to conserve as much bandwidth as possible.
+fetch("some.json", {cache: "force-cache"})
+ .then(function(response) { /* consume the response */ });</pre>
+
+<h2 id="Specifications">Specifications</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('Fetch','#dom-request-cache','cache')}}</td>
+ <td>{{Spec2('Fetch')}}</td>
+ <td>Initial definition</td>
+ </tr>
+ </tbody>
+</table>
+
+<h2 id="Browser_compatibility">Browser compatibility</h2>
+
+
+
+<p>{{Compat("api.Request.cache")}}</p>
+
+<h2 id="See_also">See also</h2>
+
+<ul>
+ <li><a href="/en-US/docs/Web/API/ServiceWorker_API">ServiceWorker API</a></li>
+ <li><a href="/en-US/docs/Web/HTTP/Access_control_CORS">HTTP access control (CORS)</a></li>
+ <li><a href="/en-US/docs/Web/HTTP">HTTP</a></li>
+</ul>