Password strength meter (Gravity Forms 1.6.12)

// http://www.gravityhelp.com/forums/topic/password-advanced-field-enable-password-strength-and-minimum-strength#post-182157
// from Gravity Forms version 1.6.12
// wp-content/plugins/gravityforms/js/gravityforms.js starting on line 514
//
// Password strength meter
function gformPasswordStrength(password1, password2) {
    var shortPass = 1, badPass = 2, goodPass = 3, strongPass = 4, mismatch = 5, symbolSize = 0, natLog, score;

    if(password1.length <=0)
        return "blank";

    // password 1 != password 2
    if ( (password1 != password2) && password2.length > 0)
        return "mismatch";

    //password < 4
    if ( password1.length < 4 )
        return "short";

    if ( password1.match(/[0-9]/) )
        symbolSize +=10;
    if ( password1.match(/[a-z]/) )
        symbolSize +=26;
    if ( password1.match(/[A-Z]/) )
        symbolSize +=26;
    if ( password1.match(/[^a-zA-Z0-9]/) )
        symbolSize +=31;

    natLog = Math.log( Math.pow(symbolSize, password1.length) );
    score = natLog / Math.LN2;

    if (score < 40 )
        return "bad";

    if (score < 56 )
        return "good";

    return "strong";

}