A simple javascript function to validate email address

This is a simple javascript funciton which validates the entered email address. You can add this to your javascript library functions. Know more information from this link

 

//calling the method
btnSubmit.Attributes.Add("OnClick", "javascript:return CheckEmail('txtEmail');")
  
//function CheckEmail
                function CheckEmail(ControlID)
	                {
	                    var str=document.getElementById(ControlID).value;	 
		                if (str != "" )
		                {
		                    
			                var at="@"
			                var dot="."
			                var lat=str.indexOf(at)
			                var lstr=str.length
			                var ldot=str.indexOf(dot)
                							
				                if (str.indexOf(at)==-1)
				                {
					                alert("Invalid E-mail ID");
					                document.getElementById(ControlID).focus();					
					                return false;
				                }

				                if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr)
				                {
					                alert("Invalid E-mail ID");	
					                document.getElementById(ControlID).focus();					
					                return false;
				                }

				                if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr)
				                {
					                alert("Invalid E-mail ID");
					                document.getElementById(ControlID).focus();						
					                return false;
				                }

				                if (str.indexOf(at,(lat+1))!=-1)
				                {
					                alert("Invalid E-mail ID");
					                document.getElementById(ControlID).focus();	
					                return false;
				                }

				                if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot)
				                {
					                alert("Invalid E-mail ID");
					                document.getElementById(ControlID).focus();	
					                return false;
				                }

				                if (str.indexOf(dot,(lat+2))==-1)
				                {
					                alert("Invalid E-mail ID");
					                document.getElementById(ControlID).focus();	
					                return false;
				                }

				                if (str.indexOf(" ")!=-1)
				                {
					                alert("Invalid E-mail ID");
					                document.getElementById(ControlID).focus();	
					                return false;
				                }
 			                return true;
 		                }
		           }