form.js

function validation(){

      var username = document.getElementById('username').value;
      var pass = document.getElementById('pass').value;
      var confirmpass = document.getElementById('conpass').value;
      var mobileNumber = document.getElementById('mobileNumber').value;
      var emails = document.getElementById('emails').value;

      if(username == ""){
        document.getElementById('username').innerHTML =" ** Please fill the username field";
        alert ( "Please fill in the 'Your Name' box." );
        return false;
      }
      if((username.length <= 2) || (username.length > 20)) {
        document.getElementById('username').innerHTML =" ** Username lenght must be between 2 and 20";
        return false; 
      }
      if(!isNaN(username)){
        document.getElementById('username').innerHTML =" ** only characters are allowed";
        return false;
      }





      if(pass == ""){
        document.getElementById('passwords').innerHTML =" ** Please fill the password field";
        return false;
      }
      if((pass.length <= 5) || (pass.length > 20)) {
        document.getElementById('passwords').innerHTML =" ** Passwords lenght must be between  5 and 20";
        return false; 
      }


      if(pass!=confirmpass){
        document.getElementById('confrmpass').innerHTML =" ** Password does not match the confirm password";
        return false;
      }



      if(confirmpass == ""){
        document.getElementById('confrmpass').innerHTML =" ** Please fill the confirmpassword field";
        return false;
      }




      if(mobileNumber == ""){
        document.getElementById('mobileno').innerHTML =" ** Please fill the mobile NUmber field";
        return false;
      }
      if(isNaN(mobileNumber)){
        document.getElementById('mobileno').innerHTML =" ** user must write digits only not characters";
        return false;
      }
      if(mobileNumber.length!=10){
        document.getElementById('mobileno').innerHTML =" ** Mobile Number must be 10 digits only";
        return false;
      }



      if(emails == ""){
        document.getElementById('emailids').innerHTML =" ** Please fill the email idx` field";
        return false;
      }
      if(emails.indexOf('@') <= 0 ){
        document.getElementById('emailids').innerHTML =" ** @ Invalid Position";
        return false;
      }

      if((emails.charAt(emails.length-4)!='.') && (emails.charAt(emails.length-3)!='.')){
        document.getElementById('emailids').innerHTML =" ** . Invalid Position";
        return false;
      }
    }