XML HTTP Request

The XMLHttpRequest Object

The XMLHttpRequest object is used to exchange data with a server behind the scenes.

The XMLHttpRequest object is a developer's dream, because you can:

• Update a web page without reloading the page
• Request data from a server after the page has loaded
• Receive data from a server after the page has loaded
• Send data to a server in the background

To learn more about the XMLHttpRequest object, study our XML DOM tutorial.

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XMLHttpRequest Example

When you type a character in the input field below, an XMLHttpRequest is sent to the server - and name suggestions are returned (from a file on the server):

Type a letter in the input box: First Name Suggestions:

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Create an XMLHttpRequest Object

All modern browsers (IE7+, Firefox, Chrome, Safari, and Opera) have a built-in XMLHttpRequest object.

Syntax for creating an XMLHttpRequest object:

xmlhttp=new XMLHttpRequest();

Old versions of Internet Explorer (IE5 and IE6) use an ActiveX Object:

xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");

In the next chapter, we will use the XMLHttpRequest object to retrieve XML information from a server.