Password validation using regular expressions. Returns an error message based on what is missing/wrong with the user's password (or returns "ok"). Password must contain at least one letter and one number, must be between 6 and 50 characters in length, and may contain certain special characters (such as !, #, &, etc.).

password.js

function ValidatePassword(str){

    if (str.length < 6) {
        return("Password is too short. Must be at least 6 characters.");
    } else if (str.length > 50) {
        return("Password is too long. Must be no more than 50 characers.");
    } else if (str.search(/\d/) == -1) {
        return("Password must contain at least one number.");
    } else if (str.search(/[a-zA-Z]/) == -1) {
        return("Password must contain at least one letter.");
    } else if (str.search(/[^a-zA-Z0-9\!\@\#\$\%\^\&\*\(\)\_\+]/) != -1) {
        return("Password contains a character that is not allowed. Please try again.");
    }
    return("ok");
}