Left Pad String

function leadingZeros(num, totalChars, padWith) {
	num = num + "";
	padWith = (padWith) ? padWith : "0";
	if (num.length < totalChars) {
		while (num.length < totalChars) {
			num = padWith + num;
		}
	} else {}
 
	if (num.length > totalChars) { //if padWith was a multiple character string and num was overpadded
		num = num.substring((num.length - totalChars), totalChars);
	} else {}
 
	return num;
}
 
alert(leadingZeros("asdf", 10, "0"));