XMLHttpRequest.onreadystatechange

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.

The readystatechange event will not be fired when an XMLHttpRequest request is cancelled with the abort() method.

Syntax

XMLHttpRequest.onreadystatechange = callback;

Values

• callback is the function to be executed when the readyState changes.

Example

var xhr = new XMLHttpRequest(),
    method = "GET",
    url = "https://developer.mozilla.org/";

xhr.open(method, url, true);
xhr.onreadystatechange = function () {
        if(xhr.readyState === XMLHttpRequest.DONE && xhr.status === 200) {
            console.log(xhr.responseText);
        }
    };
xhr.send();

Specifications

Specification	Status	Comment
XMLHttpRequest	Living Standard	WHATWG living standard

Browser compatibility

[1] Internet Explorer version 5 and 6 supported ajax calls using ActiveXObject().