Ajax Example : Explanation



Previously we have learnt about the basic and working of the Ajax.

Recommanded Reading : How to execute the Ajax on the local machine ?

Ajax Example :

In this tutorial we will be learning the basic structure of the Ajax using the simple example.

<!DOCTYPE html>
<html>

<head>
<script>
function showMsg() {
   var xmlhttp;
   
   // code for IE7+, Firefox, Chrome, Opera, Safari
   if (window.XMLHttpRequest) { 
      xmlhttp = new XMLHttpRequest();
   } else { // code for IE6, IE5
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
   }
   
   xmlhttp.onreadystatechange = function () {
      if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
         document.getElementById("msgDiv").innerHTML = 
                                        xmlhttp.responseText;
      }
   }
   
   xmlhttp.open("GET", "msg.txt", true);
   xmlhttp.send();
}
</script>
</head>

<body>

  <div id="msgDiv">
    <h2>AJAX will change this text</h2>
  </div>
  <button onclick="showMsg()">Show Message</button>

</body>

</html>

Explanation :

In the above program we have two different sections –

<div id="msgDiv">
    <h2>AJAX will change this text</h2>
</div>
<button onclick="showMsg()">Show Message</button>

First is div section and another is button.

Section Explanation
Div Section Div section is used to display the response obtained from the server.
Button Button will trigger the Ajax call by calling the showMsg() function.

We need to add a <script> tag to the page’s head section. The script section contains the showMsg() function:

<head>
<script>
function loadXMLDoc()
{
 // AJAX Script
}
</script>
</head>

In the next chapter we will be learning about the XMLHttpRequest of Ajax.