Ne vidim problem:
http://www.w3schools.com/jsref/jsref_obj_date.asp
Code:
String.prototype.padLeft = function(l,c) {return Array(l-this.length+1).join(c||" ")+this}
var hour = currentTime.getHours().toString().padLeft(2, '0');
var minute = currentTime.getMinutes().toString().padLeft(2, '0');
var second = currentTime.getSeconds().toString().padLeft(2, '0');
var time = hour + ":" + minute + ":" + second;
http://jsfiddle.net/om31an6h/