Format a Number, Exactly Two in Length?

Question

I have an integer that is less then 100 and is printed to an HTML page with JavaScript. How do I format the integer so that it is exactly two digits long? For example:

Answer 1

function padLeft(a, b) {
    var l = (a + '').length;
    if (l >= b) {
        return a + '';
    } else {
        var arr = [];
        for (var i = 0; i < b - l ;i++) {
            arr.push('0');
        }
        arr.push(a);
        return arr.join('');
    }
}