AJAX XMLHttpRequest
The keystone of AJAX is the XMLHttpRequest object.
AJAX uses the XMLHttpRequest object
To get or send information from/to a database or a file on the server with
traditional JavaScript, you will have to make an
HTML form, and a user will have to click
the "Submit" button to send/get the information, wait for the server to respond, then a new page will load with the
results. Because the server returns a new page each
time the user submits input, traditional web applications can
run slowly and tend to be less user-friendly.
With AJAX, your JavaScript communicates directly with the server, through the
JavaScript XMLHttpRequest object.
With the XMLHttpRequest object, 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 request pages, or send data to a
server in the background.
The XMLHttpRequest object is supported in all major browsers (Internet Explorer,
Firefox, Chrome, Opera, and Safari).
AJAX - Browser support
All new browsers use the built-in JavaScript XMLHttpRequest object to create
an XMLHttpRequest object (IE5 and IE6 uses an ActiveXObject).
The JavaScript code for creating an XMLHttpRequest object:
if (window.XMLHttpRequest)
{
// code for IE7+, Firefox, Chrome, Opera, Safari
return new XMLHttpRequest();
}
if (window.ActiveXObject)
{
// code for IE6, IE5
return new ActiveXObject("Microsoft.XMLHTTP");
} |
The next chapter shows how to use the XMLHttpRequest object to communicate with
a PHP server.
More about the XMLHttpRequest object
If you want to read more about the XMLHttpRequest, visit our
AJAX tutorial.
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