Alphanumeric email validation in javascript

Question

I'm using a regex below to validate email to accept alphanumeric characters. It works in the following cases

1) Must contain atleast one alphabets 2) allow alphanumeric 3) allow special characters .-and _

Regular Expression:

/^([a-zA-Z0-9])(([a-zA-Z0-9])*([\\._-])?([a-zA-Z0-9]))*@(([a-zA-Z0-9\\-])+(\\.))+([a-zA-Z]{2,4})+$/i

Cases:

1111@gmail.com - allow

aaaa@gmail.com - allow

aa1_aa@gmail.com - allow

Output expected:

1111@gmail.com - not allow because it does not contain alphabets before @

aaaa@gmail.com - allow

a1@gmail.com - allow

1a@gmail.com - allow

aa1_aa@gmail.com - allow

Hers is jsfiddle Demo

Answer 1

Your regex will do the job, just add this at the beginning

(?=[^@]*[A-Za-z])

making your final regex like this:

/^(?=[^@]*[A-Za-z])([a-zA-Z0-9])(([a-zA-Z0-9])*([\\._-])?([a-zA-Z0-9]))*@(([a-zA-Z0-9\\-])+(\\.))+([a-zA-Z]{2,4})+$/i

(?=exp) is positive look-ahead. It will try to find the expression without taking it into match. look-ahead actually matches characters, but then gives up the match.

(?=[^@]*[A-Za-z]) : will match [^@]*[A-Za-z] , meaning anything other than @ followed by a alphabet. So actually it will match if at least one alphabet is present in the part before @

You can refer this for look-ahead and look-behind

Answer 2

Here is the JavaScript code:

var email_to_check = "1111@gmail.com";
email_check=email_to_check.substring(0,email_to_check.lastIndexOf("@"));
var isnum = /^\d+$/.test(email_check);
var email_regex = /^([a-zA-Z0-9!@#$%^&*(){}|:"<>?\/';\\+\-~]*@[a-zA-z]+\.[a-zA-z]+)$/;
email_test = email_regex.test(email_to_check);
if(isnum){
alert("You must enter aleast an Alphabet !")    
}else{
    if(email_test){
           /* code if email is right :) */
        alert("This is corrrect email !")
    }else{

    alert("Enter valid email address !");
    }
   }

Remove the special char which you don't want in your checklist.