SOURCE

var target = '2ac';
var result = 0;
var base = 10;
var arr = [
    '0','1','2','3','4','5','6','7','8',
    '9','a','b','c','d','e','f','g','h',
    'i','j','k','l','m','n','o','p','q',
    'r','s','t','u','v'
];

var len = target.length;
for(var i = 0; i < len; i++){
    if(/\d/.test(target[i])){
        result += Number(target[i]) * Math.pow(base,len - 1 - i);
    }else{
        result += arr.indexOf(target[i]) * Math.pow(base,len - 1 - i);
    }
}
console.log(result);