Question

I am trying to validate the password using regular expression. The password is getting updated if we have all the characters as alphabets. Where am i going wrong ? is the regular expression right ?

function validatePassword() {
    var newPassword = document.getElementById('changePasswordForm').newPassword.value;
    var minNumberofChars = 6;
    var maxNumberofChars = 16;
    var regularExpression  = /^[a-zA-Z0-9!@#$%^&*]{6,16}$/;
    alert(newPassword); 
    if(newPassword.length < minNumberofChars || newPassword.length > maxNumberofChars){
        return false;
    }
    if(!regularExpression.test(newPassword)) {
        alert("password should contain atleast one number and one special character");
        return false;
    }
}

Answer 1

Use positive lookahead assertions:

var regularExpression = /^(?=.*[0-9])(?=.*[!@#$%^&*])[a-zA-Z0-9!@#$%^&*]{6,16}$/;

Without it, your current regex only matches that you have 6 to 16 valid characters, it doesn’t validate that it has at least a number, and at least a special character. That’s what the lookahead above is for.

• (?=.*[0-9]) – Assert a string has at least one number;
• (?=.*[!@#$%^&*]) – Assert a string has at least one special character.