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.

Example

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

xhr.open(method, url, true);
xhr.onreadystatechange = function () {
  if(xhr.readyState === 4 && xhr.status === 200) {
    console.log(xhr.responseText);
  }
};
xhr.send();

Specifications

Specification Status Comment
XMLHttpRequest Living Standard WHATWG living standard

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support 1Edge Full support 12Firefox Full support 1IE Full support 7
Notes
Full support 7
Notes
Notes Internet Explorer version 5 and 6 supported ajax calls using ActiveXObject()
Opera Full support YesSafari Full support 1.2WebView Android Full support 1Chrome Android Full support 18Edge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS ? Samsung Internet Android Full support Yes

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown
See implementation notes.
See implementation notes.

Document Tags and Contributors

Last updated by: SteveVS,