Calling Web Service using XMLHTTP Object

Follow the steps to invoke a webservice using a XMLHTTP object in javascript

Step  1: Create a soap envelope for the requested method.

 var envelope = <The above string>;

Step 2: Create Instance of XMLHTTP Object

Now in the Javascript method create an instance of the XMLHTTP object

 

 Step 3: Prepare the Webservice Request

 As shown above the url points the target webservice which is Service.asmx file and named of the method is HelloWorld. The syntax to be used

http://<Host Name>/<Virtual Directory>/<Webservice>/Method Name

in the next line we are initiating a POST request for the webservice url.

Step 4: Handling the Callback

Here when the response from the web service returns it just display the return string in alert box.

Step 5: Sending the  Request

 

As shown above, the send message is send with the envelope  for the Web Method prepare in the Step 1.

Step 6: Executing the Web Service

Refer to this link for more  http://support.microsoft.com/default.aspx/kb/893659