The XMLHttpRequest Object
The XMLHttpRequest object is supported in Internet Explorer 5.0+, Safari 1.2, Mozilla 1.0 / Firefox, Opera 9, and Netscape 7.
What is an HTTP Request?
With an HTTP request, a web page can make a request to, and get a response from a web server - without reloading the page. The user will stay on the same page, and he or she will not notice that scripts might request pages, or send data to a server in the background.
By using the XMLHttpRequest object, a web developer can change a page with data from the server after the page has loaded.
Google Suggest is using the XMLHttpRequest object to create a very dynamic web interface: When you start typing in Google's search box, a JavaScript sends the letters off to a server and the server returns a list of suggestions.
Is the XMLHttpRequest Object a W3C Standard?
The XMLHttpRequest object is a JavaScript object, and is not specified in any W3C recommendation.
However, the W3C DOM Level 3 "Load and Save" specification contains some similar functionality, but these are not implemented in any browsers yet. So, at the moment, if you need to send an HTTP request from a browser, you will have to use the XMLHttpRequest object.
var xmlhttp=new XMLHttpRequest()
var xmlhttp=new ActiveXObject("Microsoft.XMLHTTP")
<script type="text/javascript">
var xmlhttp
function loadXMLDoc(url)
{
xmlhttp=null
// code for Mozilla, etc.
if (window.XMLHttpRequest)
{
xmlhttp=new XMLHttpRequest()
}
// code for IE
else if (window.ActiveXObject)
{
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP")
}
if (xmlhttp!=null)
{
xmlhttp.onreadystatechange=state_Change
xmlhttp.open("GET",url,true)
xmlhttp.send(null)
}
else
{
alert("Your browser does not support XMLHTTP.")
}
}
function state_Change()
{
// if xmlhttp shows "loaded"
if (xmlhttp.readyState==4)
{
// if "OK"
if (xmlhttp.status==200)
{
// ...some code here...
}
else
{
alert("Problem retrieving XML data")
}
}
}
</script>
