readystatechange

Summary

Fires whenever the readyState of the request changes. Mostly used to determine whether the body of the response is available for handling.

Overview Table

The following script demonstrates how to set an asynchronous event handler that alerts the user when the readyState property of the request reaches complete (4). Note that you must set the event handler after calling open, which resets all properties of the XMLHttpRequest object to their initial value.

function reportStatus() {
    if (xhr.readyState == 4 /* complete */) {
        if (xhr.status == 200 || xhr.status == 304) {
            console.log("Transfer complete.");
        }
        else {
            // error occurred
        }
    }
}
var xhr = new XMLHttpRequest();
xhr.open("GET", "http://localhost/test.xml", true);
xhr.onreadystatechange = reportStatus;
xhr.send();

Related specifications

W3C XMLHttpRequest Specification

W3C Working Draft

Attributions

• Microsoft Developer Network: Windows Internet Explorer API reference Article