JavaScript format number to day with always 3 digits [duplicate]

Answer 1

How about:

 zeroFilled = ('000' + x).substr(-3)

For arbitrary width:

 zeroFilled = (new Array(width).join('0') + x).substr(-width)

As per comments, this seems more accurate:

lpad = function(s, width, char) {
    return (s.length >= width) ? s : (new Array(width).join(char) + s).slice(-width);
}