My onReadyStateChange is never called,why?

Question

my code is simple.

function useXMLHttpRequest() {
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("POST", "test.ashx", false);
xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8");
xmlhttp.onReadyStateChange = function () {
    alert("ss");
};
xmlhttp.send("i=5");
alert(xmlhttp.responseText);

}

when I call useXMLHttpRequest.Yes ,it alerts the xmlhttp.responseText's value. but it doesn't alert("ss"). Both in IE9 and firefox. Anyone can tell me what's worng?

score 3 · Accepted Answer · answered Oct 26 '12 at 05:33

3

JavaScript (and all other languages that I know of) are case-sensitive, so onreadystatechange is not the same as onReadyStateChange.

Try this instead:

xmlhttp.onreadystatechange = function() {
    alert("ss");
};

answered Oct 26 '12 at 05:33

Blender

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yes,i found this problem after i post this question.What a foolish me. – roast_soul Oct 26 '12 at 05:38

score 0 · Answer 2 · answered Oct 26 '12 at 05:37

You have

xmlhttp.open("POST", "test.ashx", false);

3rd parameter is false, which means that you are using synchronous request. For such requests onreadystatechange does not work and is discouraged to use it. Anyway, your request will not go further until complete completion, so alert(xmlhttp.responseText); immediately after xmlhttp.send("i=5"); works correctly and there is no need to handle request state change event.

See more here and here.

My onReadyStateChange is never called,why?

2 Answers2