Small JavaScript function to left pad a number

Number.padLeft.js

if (!Number.prototype.padLeft) {
    // Pad the left of a number with a character
    Number.prototype.padLeft = function (len, chr) {
        var self = Math.abs(this) + '';
        return (this < 0 && '-' || '') +
            (String(Math.pow(10, (len || 2) - self.length))
                .slice(1).replace(/0/g, chr || '0') + self);
    };
}