Generate Promo Code / Random String

function generateRandomPromo() {     length = 6;     chars = '#aA';     var mask = '';     if (chars.indexOf('a') > -1) mask += 'abcdefghijklmnopqrstuvwxyz';     if (chars.indexOf('A') > -1) mask += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';     if (chars.indexOf('#') > -1) mask += '0123456789';     if (chars.indexOf('!') > -1) mask += '~`!@#$%^&amp;*()_+-={}[]:";\'<>?,./|\\';     var result = '';     for (var i = length; i > 0; --i) result += mask[Math.round(Math.random() * (mask.length - 1))];     $('#EventPromocode_promocode').val(result); }