为什么我不能从 Ajax 函数返回 responseText?

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这是我的 Ajax 函数的一部分.由于某种我无法弄清楚的原因，我可以alert() responseText 但不能return responseText.有人可以帮忙吗?我需要在另一个函数中使用该值.

Here is part of my Ajax function. For some reason that I cannot figure out, I am able to alert() responseText but not able to return responseText. Can anybody help? I need that value to be used in another function.

http.onreadystatechange = function(){ if( http.readyState == 4 && http.status == 200 ){ return http.responseText; } }

推荐答案

您将无法处理从异步回调返回的返回值.你应该直接在回调中处理responseText，或者调用一个辅助函数来处理响应:

You will not be able to handle the return value that you are returning from your asynchronous callback. You should handle the responseText within the callback directly, or call a helper function to handle the response:

http.onreadystatechange = function () { if (http.readyState == 4 && http.status == 200) { handleResponse(http.responseText); } } function handleResponse (response) { alert(response); }