js二进制和十进制相互转换

<script>

function ten(num) {
    var sum = 0, tmp = 1;
    for (var i=0, len=num.length; i<len; i++) {
        if (num[i] == 1) {
            tmp = 1;
            for (var j=i+1; j<len; j++) {
                 tmp *= 2;
            }
            sum += tmp;
        }
    }
    return sum;
}

var num1=a=0, arr=[];
function bin(num) {
    len = arr.length;
    arr[len] = num%2;
    a = parseInt(num/2);
    if (a >= 2) {
        bin(a);
    } else if (a == 1) {
        bin(a);
    }
}

bin(1100100);
num1 = arr.reverse().join('');
console.log(num1);
console.log(ten(num1));
</script>