AJAX Browsers

To create this important Ajax object, you have to use a special programming technique known as "try and catch". Basically it attempts to "try" a piece of code and if that piece cause an error it "catches" the error and keeps going. Normally when an error occurs the code will stop running, however, the "catch" eats up the error that was generated in the try block and lets the code continue

In the code below we are going to "try" three different ways to make a new XMLHttpRequest object. Every time we fail and get errors, we will catch the errors and try the next a different command.

Note: If our "try" is successful then the "catch" code will not be run as it is only used when there is an error.

In the above Javascript code, we tried three times to make our XMLHttpRequest object. Our first attempt was :

• ajaxRequest = new XMLHttpRequest();

is for the Opera 8.0+, Firefox and Safari browser. If that fails we try two more times to make the correct object for an Internet Explorer with:

• ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
• ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");>

If that doesn't work, then they are using a very outdated browser that doesn't support XMLHttpRequest, which means it doesn't support Ajax.

Most likely though, our variable ajaxRequest will now be set to whatever XMLHttpRequest standard the browser use and we can start sending data to the server.

This class allows to interact with the servers, thanks to its methods and attributes.