Java Technology: 05. AJAX - Browser Support

All the available browsers can not support AJAX. Here is the list of major browsers which support AJAX.

Mozilla Firefox 1.0 and above
Netscape version 7.1 and above
Apple Safari 1.2 and above.
Microsoft Internet Exporer 5 and above
Konqueror
Opera 7.6 and above

So now when you write your application then you would have to take care of the browsers who do not support AJAX.
NOTE: When we are saying that browser does not support AJAX it simply means that browser does not support creation of Javascript object XMLHttpRequest object.

Writing Browser Specific Code

Simple way of making your source code compatible to a browser is to use try...catch blocks in your javascript.

<html>
<body>
<script language="javascript" type="text/javascript">
<!-- 
//Browser Support Code
function ajaxFunction(){
 var ajaxRequest;  // The variable that makes Ajax possible!
 
 try{
   // Opera 8.0+, Firefox, Safari
   ajaxRequest = new XMLHttpRequest();
 }catch (e){
   // Internet Explorer Browsers
   try{
      ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
   }catch (e) {
      try{
         ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
      }catch (e){
         // Something went wrong
         alert("Your browser broke!");
         return false;
      }
   }
 }
}
//-->
</script>
<form name='myForm'>
Name: <input type='text' name='username' /> <br />
Time: <input type='text' name='time' />
</form>
</body>
</html>

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

ajaxRequest = new XMLHttpRequest();

is for the Opera 8.0+, Firefox and Safari browsers. If that fails we try two more times to make the correct object for an Internet Explorer browser 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 also means it doesn't support Ajax.
Most likely though, our variable ajaxRequest will now be set to whatever XMLHttpRequest standard the browser uses and we can start sending data to the server.
Next section will give you step by step explaination of AJAX work flow.

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Thứ Năm, 28 tháng 2, 2013

05. AJAX - Browser Support

Writing Browser Specific Code

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