Math.round.js

const { round, floor, ceil } = Math;
let correct = [0,0,0];
function test(dpr, dim) {
	let clientWidth = round(dim / dpr);
	let scaled = clientWidth * dpr;
	if (round(scaled) === dim) {
		correct[0]++;
	}
	if (floor(scaled) === dim) {
		correct[1]++;
	}
	if (ceil(scaled) === dim) {
		correct[2]++;
	}
}

function testWidths(widths) {
	let weighted_correct = [0,0,0];
	let weighted_total = 0;

	// from https://arh.antoinevastel.com/reports/stats/deviceType_screen-devicePixelRatio_report.html
	[
		[1, 0.8888888955116272],
		[8, 0.8955223880597015],
		[5, 0.8999999761581421],
		[1, 0.9599999785423279],
		[1, 0.8500000238418579],
		[5, 1.125],
		[1, 1.7647058823529411],
		[2, 1.7999999523162842],
		[176, 1.5],
		[362, 1.25],
		[1, 1.7000000476837158],
		[1, 1.700084924697876],
		[4, 1.3043478260869565],
		[1, 1.399999976158142],
		[1, 1.3953488372093024],
		[2, 1.3333333333333333],
		[1, 1.1145833730697632],
		[2, 1.375],
		[1, 1.1041666269302368],
		[14, 1.100000023841858],
		[5, 1.5625],
		// [7615, 1],
		[3, 1.2999999523162842],
		[2, 1.600000023841858],
		[2, 1.5789473684210527],
		[5, 1.2],
		[1, 1.3312500715255737],
		[22, 1.75],
		[3, 2.2222222222222223],
		[1, 2.25],
		[4, 2.608695652173913],
		[25, 2.75],
		// [1284, 2],
		[2, 2.1000001430511475],
		[12, 2.549999952316284],
		[1, 2.1875],
		[15, 2.5],
		[1, 2.0001001358032227],
		[1, 2.3375000953674316],
		[47 , 2.625],
		// [208, 3],
		[19, 3.5],
		[2, 3.4000000953674316],
		// [33, 4],
	].forEach((pair) => {
		let [count, dpr] = pair;
		widths.forEach(test.bind(null, dpr));
		for (let ii = 0; ii < correct.length; ++ii) {
			weighted_correct[ii] += correct[ii] / widths.length * count;
			correct[ii] = 0;
		}
		weighted_total += count;
	});
	let labels = ['Math.round', 'Math.floor', 'Math.ceil'];
	console.log(weighted_correct.map((a, idx)=>labels[idx] + ': ' + (100*a / weighted_total).toFixed(1)).join('\n'));
}

let widths = [];
for (let ii = 1; ii < 1000; ++ii) {
	widths.push(ii);
}
testWidths(widths);
console.log('');
testWidths([480, 640, 768, 800, 1024, 1080, 1280, 1920, 2560, 3840]);

Output.txt

All resolutions:
  Math.round: 69.1
  Math.floor: 56.8
  Math.ceil: 56.6

Common resolutions only:
  Math.round: 80.9
  Math.floor: 70.6
  Math.ceil: 76.3