data validation
 

How to do data validation while submitting form?

You validate your data with javascript, before sending them to the server.
Example:

And in javascript:

function validate_contact(){
var name=jQuery.trim($('#name').val());
var email=jQuery.trim($('#email').val());
var comments=jQuery.trim($('#comments').val());

if (name=='' || name.length<3)
{alert ('Please enter your name');return false;}
if (/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/.test(email)==false)
{alert('Please enter valid email address');return false;}
if (comments.length<1)
{alert('Please enter your comments');return false;}

}