Simple timer function

demo.js

const {start, measure, create} = require('./timer.js')

const MAX=1000

var seed = Math.random()*1000;
function random() {
    var x = Math.sin(seed++) * 10000;
    return x - Math.floor(x);
}

start('hello')
let to1 = random()*MAX
let to2 = random()*MAX
setTimeout(()=>{
  console.log(`task hello took ${measure('hello')}ms (${to1})`)
},to1)

let bye = create('bye')
setTimeout(()=>{
  console.log(`task bye took ${bye.measure()}ms (${to2})`)
},to2)

timer.js

const { performance } = require('perf_hooks')

class TimerError extends Error {}

const timers={}

function start(name){
	timers[name] = performance.now()
	return timers[name]
}

function measure(name){
	if(!(name in timers)) throw new TimerError(`Timer with name '${name}' was never started.`)
	return performance.now() - timers[name]
}


/**
 * Create a named timer
 *
 * @param {String} name The name of the timer
 * @returns {Object}
 */
function create(name){
	start(name)
	return {
		start(){ return start(name) },
		measure(){ return measure(name) },
	}
}

module.exports = {
	create,
	start,
	measure
}