The XMLHttpRequest Object

What is the XMLHttpRequest Object?

The XMLHttpRequest object is the developers dream, because you can:

* Update a web page with new data 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

The XMLHttpRequest object is supported in all modern browsers.

Why Use Async=true?

Our examples use "true" in the third parameter of open().

This parameter specifies whether the request should be handled asynchronously.

True means that the script continues to run after the send() method, without waiting for a response from the server.

The onreadystatechange event complicates the code. But it is the safest way if you want to prevent the code from stopping if you don't get a response from the server.

By setting the parameter to "false", your can avoid the extra onreadystatechange code. Use this if it's not important to execute the rest of the code if the request fails.