for loops vs. every

gistfile1.txt

$ node index.js
for: 1196073 hz
every: 417669 hz
Fastest is for
$

index.js

// yarn add benchmark lodash
// yarn index.js
const isEqual = require('lodash/isEqual');
const assert = require('assert');
const Benchmark = require('benchmark');


function compareKeySubsetForLoop(objects, keys, comparator = isEqual) {
  if (objects.length <= 1) return true;
  if (keys.length === 0) return true;
  for (let keyIndex = 0; keyIndex < keys.length; keyIndex += 1) {
    const key = keys[keyIndex];
    const cmpVal = objects[0][key];
    for (let objIndex = 1; objIndex < objects.length; objIndex += 1) {
      if (!comparator(objects[objIndex][key], cmpVal)) {
        // Early-out at the first mismatch.
        return false;
      }
    }
  }
  return true;
}

function compareKeySubsetEvery(objects, keys, comparator = isEqual) {
  if (objects.length <= 1) return true;
  if (keys.length === 0) return true;
  return keys.every((key) => {
    const cmpVal = objects[0][key];
    return objects.every(obj => comparator(obj[key], cmpVal));
  });
}

const manyObjects = [
  {a: 1, b: 2},
  {a: 1, b: 2, c: 4},
  {a: 1, b: 2, c: 4, d: 5},
  {a: 1, b: 2},
  {a: 1, b: 2, c: 4},
  {a: 1, b: 2, c: 4, d: 5},
  {a: 1, b: 2},
  {a: 1, b: 2, c: 4},
  {a: 1, b: 2, c: 4, d: 5},
];

const twoObjects = [
  {a: 1, b: 2},
  {a: 1, b: 3},
];

const noCommonAObjects = [
  {a: 1, b: 2},
  {a: 1, b: 3},
  {a: 2, b: 3},
];

function testFunc(compareKeySubset) {
  assert(compareKeySubset(twoObjects, ['a']));
  assert(!compareKeySubset(twoObjects, ['b']));
  assert(compareKeySubset(manyObjects, ['a']));
  assert(compareKeySubset(manyObjects, ['a', 'b']));
  assert(!compareKeySubset(noCommonAObjects, ['a']));
  assert(compareKeySubset([], ['a']));
  assert(compareKeySubset(twoObjects, []));
}

var suite = new Benchmark.Suite;
suite.add('for', () => testFunc(compareKeySubsetForLoop));
suite.add('every', () => testFunc(compareKeySubsetEvery));
suite.on('cycle', (event) => console.log(`${event.target.name}: ${Math.round(event.target.hz)} hz`));
suite.on('complete', () => console.log('Fastest is ' + suite.filter('fastest').map('name')));
suite.run();