Typescript class for detecting and reacting to page idle state, still needs touch detection etc.

IdleTimer.ts

class IdleTimer
{
    timer: any;
    timeIncrement: number = 1000;
    timeMax: number = 10000;
    timeIdle: number = 0;
    expiryCallback: Function;
    awakeCallback: Function;
    tickCallback: Function;
    interactionMethods: string[];
    expired: boolean = false;

    constructor()
    {
        if ("ontouchstart" in document.documentElement) { console.log('yep!') };
        this.interactionMethods = ['click', 'mousemove'];
    }

    start()
    {
        this.timeIdle = 0;
        this.timer = setInterval(() => this.checkIdleTime(), this.timeIncrement);
        for (var i = 0; i < this.interactionMethods.length; i++)
        {
            document.addEventListener(this.interactionMethods[i], () => this.resetTimer());
        }
    }

    stop()
    {
        clearInterval(this.timer);
        for (var i = 0; i < this.interactionMethods.length; i++) {
            document.removeEventListener(this.interactionMethods[i], () => this.resetTimer());
        }
    }

    checkIdleTime ()
    {
        this.timeIdle += this.timeIncrement;
        if (this.timeIdle <= this.timeMax && typeof (this.tickCallback) === 'function') this.tickCallback(this.timeIdle, this.timeMax);

        if (this.expired === false && this.timeIdle > this.timeMax)
        {
            this.expired = true;
            if (typeof (this.expiryCallback) === 'function') this.expiryCallback();
        }
    }

    resetTimer()
    {
        if (this.expired === true)
        {
            this.expired = false;
            if (typeof (this.awakeCallback) === 'function') this.awakeCallback();
        }

        this.timeIdle = 0;   
    }
}

//example usage - in main js file
window.onload = function()
{
	var it = new IdleTimer();
	it.awakeCallback = function(){
		document.getElementById('status').innerHTML = "night-time...";
		document.getElementById('bird').setAttribute('class','asleep');
	};
	it.expiryCallback = function(){
		document.getElementById('status').innerHTML = "daytime!";
		document.getElementById('bird').setAttribute('class','');
	};
	/*it.tickCallback = function(time, maxtime){
		document.getElementById('status').innerHTML = ((maxtime - time)/1000) + '...';
	}	*/
	it.start();
}