Time various loop structures

results.md

Base code/idea comes from this blog post

The output:

Testing vanilla:      4.1ms
Testing lodash:      25.4ms -- 518% slower
Testing es6-for-of:   7.3ms --  78% slower
Testing forEach:      6.1ms --  48% slower
Testing map:          9.2ms -- 125% slower
Testing reverse:      3.4ms --  17% faster
Testing shift:       20.9ms -- 408% slower

test-loop-timings.js

const _ = require("lodash");
const perfy = require("perfy");

const times = {};
let baseline = 25000;
let total = 0;

const LOOPS = 100000;

function testVanilla() {
  let tmp = 0;
  const someNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
  for (let p = 0; p < LOOPS; p++) {
    for (let i = 0; i < someNumbers.length; i++) {
      tmp += someNumbers[i];
    }
  }
  total = tmp; // Set the total to check all other loops against
  console.assert(tmp === total);
}

function testLodash() {
  let tmp = 0;
  const someNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
  for (let p = 0; p < LOOPS; p++) {
    _.each(someNumbers, function(value) {
      tmp += value;
    });
  }
  console.assert(tmp === total);
}

function testES6ForOf() {
  let tmp = 0;
  const someNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
  for (let p = 0; p < LOOPS; p++) {
    for (let value of someNumbers) {
      tmp += value;
    }
  }
  console.assert(tmp === total);
}

function testForEach() {
  let tmp = 0;
  const someNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
  for (let p = 0; p < LOOPS; p++) {
    someNumbers.forEach(value => (tmp += value));
  }
  console.assert(tmp === total);
}

function testMap() {
  let tmp = 0;
  for (let p = 0; p < LOOPS; p++) {
    const someNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
    someNumbers.map(value => (tmp += value));
  }
  console.assert(tmp === total);
}

function testReverseLoop() {
  let tmp = 0;
  const someNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
  for (let p = 0; p < LOOPS; p++) {
    for (let i = someNumbers.length - 1; i >= 0; i--) {
      tmp += someNumbers[i];
    }
  }
  console.assert(tmp === total);
}

function testArrayShift() {
  let tmp = 0;
  for (let p = 0; p < LOOPS; p++) {
    const someNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
    while (someNumbers.length) {
      tmp += someNumbers.shift();
    }
  }
  console.assert(tmp === total);
}

function doTest(label, fn) {
  perfy.start(label);
  fn();
  let result = perfy.end(label);
  times[label] = result.fullMilliseconds;
}

doTest("vanilla", testVanilla);
doTest("lodash", testLodash);
doTest("es6-for-of", testES6ForOf);
doTest("forEach", testForEach);
doTest("map", testMap);
doTest("reverse", testReverseLoop);
doTest("shift", testArrayShift);

baseline = times["vanilla"];

for (let label in times) {
  const delta = Math.round(100 * ((times[label] - baseline) / baseline));
  const space2 = Math.abs(delta) >= 100 ? "" : " ";
  const space1 = times[label] >= 10 ? "" : " ";
  const analysis = delta > 0 ? ` -- ${space2}${delta}% slower` : delta < 0 ? ` -- ${space2}${-delta}% faster` : "";
  const display = _.padEnd(`Testing ${label}:`, 20);
  console.log(`${display} ${space1}${times[label].toFixed(1)}ms${analysis}`);
}