JS Performance Test: for vs for..in vs Array.some

js-loop-perf-tests.js

/* eslint max-len:0, no-console:0 */
const Benchmark = require('benchmark');
const id = require('uuid/v4');

const fileObject = {
  filename: 'ApplesApplesApplesApplesApplesApples.txt',
};

const dupes = () => ([...Array(50000)].map((x) => ({
  Filename: id(),
  FileId: id(),
})));

const testFor = () => {
  const duplicates = dupes();
  duplicates[Math.floor(Math.random() * duplicates.length)].Filename = fileObject.filename;

  const ret = fileObject;
  const dupeCount = duplicates.length;
  for (let i = 0; i < dupeCount; i += 1) {
    if (duplicates[i].Filename.toUpperCase() === fileObject.filename.toUpperCase()) {
      ret.isRevision = true;
      ret.repositoryFileId = duplicates[i].FileId;
      break;
    }
  }
  return ret;
};

const testForIn = () => {
  const duplicates = dupes();
  duplicates[Math.floor(Math.random() * duplicates.length)].Filename = fileObject.filename;

  const ret = fileObject;
  for(const d in duplicates) {
    if (duplicates[d].Filename.toUpperCase() === fileObject.filename.toUpperCase()) {
      ret.isRevision = true;
      ret.repositoryFileId = duplicates[d].FileId;
      break;
    }
  }
  return ret;
};

const testSome = () => {
  const duplicates = dupes();
  duplicates[Math.floor(Math.random() * duplicates.length)].Filename = fileObject.filename;

  const ret = fileObject;
  duplicates.some((dupe) => {
    if (dupe.Filename.toUpperCase() === fileObject.filename.toUpperCase()) {
      ret.isRevision = true;
      ret.repositoryFileId = dupe.FileId;
      return true;
    }
    return false;
  });
  return ret;
};

console.log('Tests running...');
const suite = new Benchmark.Suite();
suite
  .add('for', testFor)
  .add('for..in', testForIn)
  .add('Array.some', testSome)
  .on('cycle', (event) => {
    console.log(String(event.target));
  })
  .on('complete', function complete() {
    console.log(`Fastest is ${this.filter('fastest').map('name')}`);
  })
  .run({ async: true });
// console.log(test1());
// console.log(test2());

Surprisingly close results:

Tests running...
for x 3.98 ops/sec ±3.32% (14 runs sampled)
for..in x 3.63 ops/sec ±6.96% (14 runs sampled)
Array.some x 3.96 ops/sec ±3.14% (14 runs sampled)
Fastest is for