Password strength checker

Question

I would like to receive feedback about my code. Is there any better way to shorten the code or is it fine?

Demo

var pass_strength;
function IsEnoughLength(str,length){
    if ((str == null) || isNaN(length))
        return false;
    else if (str.length < length)
        return false;
    return true;
}
function HasMixedCase(passwd){
    if(passwd.match(/([a-z].*[A-Z])|([A-Z].*[a-z])/))
        if ( passwd.split(/[a-z]/).length >= 3 && passwd.split(/[A-Z]/).length >= 3)
            return true;
        else
            return false;
    else
        return false;
}
function HasNumeral(passwd){
    if(passwd.match(/[0-9]/))
        return true;
    else
        return false;
}
function HasSpecialChars(passwd){
    if(passwd.match(/.[!,@,#,$,%,^,&,*,?,_,~]/))
        return true;
    else
        return false;
}
function CheckPasswordStrength(pwd)
{
    if (IsEnoughLength(pwd,14) && HasMixedCase(pwd) && HasNumeral(pwd) && HasSpecialChars(pwd))
        pass_strength = "<b><font style='color:olive'>Very strong</font></b>";
    else if (IsEnoughLength(pwd,10) && HasMixedCase(pwd) && HasNumeral(pwd) && HasSpecialChars(pwd))
        pass_strength = "<b><font style='color:Blue'>Strong</font></b>";
    else if (IsEnoughLength(pwd,10) && HasMixedCase(pwd) && HasNumeral(pwd))
        pass_strength = "<b><font style='color:Green'>Medium</font></b>";
    else
        pass_strength = "<b><font style='color:red'>Weak</font></b>";
    document.getElementById('pwd_strength').innerHTML = "Password strength: " + pass_strength;
}

Answer 1

1. You can replace all of the

   if(x.match(...))
       return true;
   else
       return false;
   

   with:

   return x.match(...) !== null;
   

   or if you're content with returning a truthy/falsy value instead of proper booleans you can even simplify it to:

   return x.match(...)
   

2. IsEnoughLength is ungrammatical. I'd use IsLongEnough

3. You're mixing the password strength estimation with presentation logic. You should have one function which returns a value indicating the strength of the password and another which manipulates the DOM.
4. Use CSS classes to format the text instead of <b> and <font style=

5. Personally I wouldn't bother with argument checking in such a simple internal function. But if you do, throw an exception on programmer error, don't just return false.

   if ((str == null) || isNaN(length))
       return false;
   

   should be something like

   if (str == null)
       throw new Error("str must not be null");
   if(isNaN(length))
       throw new Error("length must be a number");
   

   (or a fancier exception class if you want)

Answer 2

As @CodesInChaos has already pointed out, the boolean expressions can be simplified, a lot. For example:

function HasMixedCase(passwd) {
    return passwd.match(/([a-z].*[A-Z])|([A-Z].*[a-z])/)
        && passwd.split(/[a-z]/).length >= 3
        && passwd.split(/[A-Z]/).length >= 3;
}
function HasNumeral(passwd) {
    return passwd.match(/[0-9]/);
}
function HasSpecialChars(passwd) {
    return passwd.match(/.[!,@,#,$,%,^,&,*,?,_,~]/);
}

In addition, I would simplify the method that checks the length like this:

function IsLongEnough(passwd, length) {
    return passwd && passwd.length > length;
}

This will only return true if passwd is not undefined and long enough.

And I dropped the validation of the length parameter. For one thing, it was unnecessary: IsLongEnough(word, undefined) and IsLongEnough(word, NaN) will always return false. For another thing, if you are calling password validation methods with invalid parameters, you are in big trouble!