A reference for looping timers.

Interval timer without setInterval().js

function mod(a,b){return((a%b)+b)%b;}
class Timer{
	constructor(callback,delay,tickBy=1,...parameters){
		this.callback=callback;
		this.duration=delay;
		this.timer=delay;
		this.tickBy=tickBy;
		this.parameters=parameters;
	}
	tick(){
		this.timer-=this.tickBy; //Subtract before the if-statement, otherwise `this.timer` would be negative.
		if(this.timer<=0){
			this.timer+=this.duration+this.tickBy; //`+=` instead of `=` because of decimal values.
			this.callback(...this.parameters);
		}
	}
}

//Usage example:
var myTimer=new Timer(
	(...x)=>{say(`Hello ${x.length>1?x.slice(0,-1).join(", ")+" and "+x[x.length-1]:x}!`);}, //Function.
	1, //Delay by seconds.
	1/60, //Decrementation.
	"John","Eric","Larry" //Parameters.
);
function update(){
	draw();
	myTimer.tick();
}

When this.timer reaches 0, it should not be set to 0 again (which would happen with integers and tick would call callback twice in a row). I find adding if(this.timer<=0){this.timer=this.duration;} after this.timer=mod(this.timer,this.duration); to be ugly, maybe we could use a modulo operation with ceil (so that it won't equal to 0 but this.duration) or a ternary operator?

{
	init:0, //Pay attention to this value.
	value:0,
	FPS:60,
	tick(){
		this.value+=1/this.FPS;
		if(this.value>=this.init){
			call(...);
			this.value-=this.init+(1/this.FPS); //`+(1/this.FPS)`, otherwise `this.value` would still be greater than 0.
		}
	}
}

🤔

I'm sure that you aren't supposed to read the this.value (also that this is based on setInterval()), since it'd either be jaggy (assigns to 0) or below 0 (subtraction assignment).