An EventHandler
that is called whenever the readyState
attribute changes. The callback is called from the user interface thread. The
XMLHttpRequest.onreadystatechange
property contains the
event handler to be called when the readystatechange
event is fired, that is every time the
readyState
property of the
XMLHttpRequest
changes.
Warning: This should not be used with synchronous requests and must not be used from native code.
Syntax
XMLHttpRequest.onreadystatechange = callback;
Values
callback
is the function to be executed when thereadyState
changes.
Examples
const xhr = new XMLHttpRequest(),
method = "GET",
url = "https://developer.mozilla.org/";
xhr.open(method, url, true);
xhr.onreadystatechange = function () {
// In local files, status is 0 upon success in Mozilla Firefox
if(xhr.readyState === XMLHttpRequest.DONE) {
var status = xhr.status;
if (status === 0 || (status >= 200 && status < 400)) {
// The request has been completed successfully
console.log(xhr.responseText);
} else {
// Oh no! There has been an error with the request!
}
}
};
xhr.send();
Specifications
Specification | Status | Comment |
---|---|---|
XMLHttpRequest | Living Standard | WHATWG living standard |
Browser compatibility
BCD tables only load in the browser