检测浏览器对跨域 XMLHttpRequests 的支持?

问题描述

我正在开发一些 Javascript，它利用 Firefox 3.5 执行跨域 XMLHttpRequests 的能力……但如果它们不受支持，我想优雅地失败.

I'm working on some Javascript that makes use of Firefox 3.5's ability to perform cross-domain XMLHttpRequests… But I'd like to fail gracefully if they aren't supported.

除了实际发出跨域请求外，还有什么方法可以检测浏览器对它们的支持吗?

Apart from actually making a cross-domain request, is there any way to detect a browser's support for them?

推荐答案

为了将来参考，完整的 CORS 特征检测应该如下所示:

For future reference, full CORS feature detection should look something like this:

//Detect browser support for CORS
if ('withCredentials' in new XMLHttpRequest()) {
    /* supports cross-domain requests */
    document.write("CORS supported (XHR)");
}
else if(typeof XDomainRequest !== "undefined"){
  //Use IE-specific "CORS" code with XDR
  document.write("CORS supported (XDR)");
}else{
  //Time to retreat with a fallback or polyfill
  document.write("No CORS Support!");
}

您可以使用 JSBin 进行现场测试，并在 IE、Firefox、Chrome、Safari 和歌剧.

You can try this test live using JSBin and see the proper response in IE, Firefox, Chrome, Safari, and Opera.

在非浏览器环境中存在一些支持跨域 XHR 但不支持 XHR2/CORS 的边缘案例.此测试不考虑这些情况.

There are some edge cases in non-browser environments that do support cross-domain XHR but not XHR2/CORS. This test does not account for those situations.

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