simple OOP exercise, stopwatch that count time between start and stop

stopwatch.js

/**
* Stopwatch onject will used for count time between start and stop time
* there are thre method on it: start, stop, reset
* and there are one property "duration"
* Implement constructor function for create object
*/
function Stopwatch () {
	let duration = 0;
	let intervalId = null;
	let isRunning = false

	this.start = function () {
		if (isRunning) {
			throw new Error("Stopwach has already started");
		} else {
			isRunning = true;
			intervalId = setInterval(()=> duration++, 1000);
		}
	}

	this.stop = function () {
		if (isRunning) {
			clearInterval(intervalId)
			isRunning = false
		} else {
			throw new Error("Stopwach is not started");
		}
	}

	this.reset = function () {
		duration = 0;
	}

	Object.defineProperty(this, "duration", {
		get: function () {return duration}
	})
}

// const sw = new Stopwatch();
// sw.start()
// sw.stop()
// sw.reset()