javascript XMLHttpRequest：如何强制缓存？
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XMLHttpRequest: How to force caching?
提问by user3631654
I'm newer to XMLHttpRequests since I've previously used jQuery's AjAX method. However I need to work in a web worker and now I have to use the classic XMLHttpRequest for performance issues.
我对 XMLHttpRequests 比较陌生，因为我以前使用过 jQuery 的 AjAX 方法。但是，我需要在网络工作者中工作，现在我必须使用经典的 XMLHttpRequest 来解决性能问题。
I'm trying to rebuild the cache-property from jquery. If cache should be disabled I add this:
我正在尝试cache从 jquery重建-property。如果缓存应该被禁用，我添加这个：
xhr.setRequestHeader("Cache-Control", "no-cache");
But what header should I set if I want to force caching (not prevent)?
但是如果我想强制缓存（而不是阻止），我应该设置什么标头？
采纳答案by Quentin
There are a variety of headers you can set to encourage caching, but they (including Cache-Controlwhich you are using incorrectly) are responseheaders that must be sent by the server and not request headers.
您可以设置多种标头来鼓励缓存，但它们（包括Cache-Control您使用不正确的标头）是必须由服务器发送的响应标头，而不是请求标头。
One such example of using Cache-Control:
使用 Cache-Control 的示例之一：
Cache-Control: max-age=3600
This Caching Tutorial for Web Authors and Webmasterscovers them in more depth.
这个面向 Web 作者和网站管理员的缓存教程更深入地介绍了它们。
回答by Franklin Yu
You can specify max-stalewithout an argument, in Cache-Controlheader of your request. From RFC 7234:
您可以在max-stale不带参数的情况下在请求的Cache-Control标头中指定。来自RFC 7234：
The
max-stalerequest directive indicates that the client is willing to accept a response that has exceeded its freshness lifetime. Ifmax-staleis assigned a value, then the client is willing to accept a response that has exceeded its freshness lifetime by no more than the specified number of seconds. If no value is assigned tomax-stale, then the client is willing to accept a stale response of any age.
该
max-stale请求指令表明该客户愿意接受已超过其使用寿命新鲜的响应。如果max-stale分配了一个值，则客户端愿意接受超过其新鲜度生命周期不超过指定秒数的响应。如果没有为 分配值max-stale，则客户端愿意接受任何年龄的陈旧响应。
