The XMLHttpRequest Object

XMLHttpRequest

• A JavaScript Class that lets you make asynchronous HTTP requests from JavaScript
• Make an HTTP request from a JavaScript event
• A call back JavaScript function is invoked at each state of the HTTP request and response

XMLHttpRequest Properties

• onreadystatechange - call back function for state changes
• readyState - the current state of the HTTP call
• responseText - the text result of the request
• responseXML - DOM xml object from the request
• status - HTTP status code of the response
• statusText - HTTP status text

XMLHttpRequest Example from sample #1:

var xmlHttpRequest;

function getXmlHttpRequestObject()
{
 if(window.ActivexObject)
 {
  return (new ActivexObject("Microsoft.XMLHTTP"));
 }
 else if( window.XMLHttpRequest)
 {
  return(new XMLHttpRequest());
 }
 else
 {
  return null; 
 }
}

function sendRequest() {
 xmlHttpRequest = getXmlHttpRequestObject();
 xmlHttpRequest.onreadystatechange = handleResponse;
 xmlHttpRequest.open("GET", "data_message.html", true);
 xmlHttpRequest.send(null);
}

function handleResponse() {
 if (xmlHttpRequest.readyState == 4) {
  alert(xmlHttpRequest.responseText);
 }
}

IE does it different

• The above example however won't work on IE
• new ActiveXOjbect("Microsoft.XMLHTTP");
• Native XMLHttpRequest support should be in IE7

Source :

• The XMLHttpObject on Apple site
• Wikipedia