Timer in Javascript

var inputElement; // html element for displaying the time


// class definition for the clock
function Clock() {
	this.timerID = null; // handler for setTimeout function
	this.timerRunning = false; // is the timer running?
	this.stopClock = stopClock; // stops the clock
	this.showTime = showTime; // displays the time
	this.startClock = startClock; // starts the clock
}	


// stops the clock if the timer is running
function stopClock () {
	if(this.timerRunning)
		clearTimeout(this.timerID);
	this.timerRunning = false;
}


// displays the time in the html input field
function showTime () {
	this.now = new Date(); // catches the actual date
	this.hours = this.now.getHours(); // takes the hours out of date
	this.minutes = this.now.getMinutes(); // takes the minutes out of date
	this.seconds = this.now.getSeconds(); // takes the seconds out of date
	this.time = ((this.hours < 10) ? "0" + this.hours : this.hours); // sets the hours
	this.time += ((this.minutes < 10) ? ":0" : ":") + this.minutes; // sets the minutes
	this.time += ((this.seconds < 10) ? ":0" : ":") + this.seconds;	// sets the seconds
	inputElement.value = this.time; // sets the time in the input field
	this.timerID = setTimeout(showTime,1000); // calls showTime in 1 second
	this.timerRunning = true; // sets timerRunning to true
}


// starts the clock
function startClock() {
	this.stopClock(); // stop it before
	this.showTime(); // calls showTime
}


// initalisation of the clock, could be called at the onload
// parameter in the body tag of the html site with the input field
// @param _inputID: the id of the input field
function initClock(_inputID) {
	var clock = new Clock(); // creats an instance of the clock
	inputElement = document.getElementById(_inputID); // gets the html element with _inputID
	clock.startClock();	// starts the clock
}