Web/API/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.

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 the readyState 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

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`onreadystatechange`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 5	Opera Full support 9	Safari Full support 1.2	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 10.1	Safari iOS Full support 1	Samsung Internet Android Full support 1.0

Legend

Full support: Full support

XMLHttpRequest.onreadystatechange by Mozilla Contributors is licensed under CC-BY-SA 2.5.