assgin_for_in_of

benchmark.js

'use strict';

const Benchmark = require('benchmark');
const benchmarks = require('beautify-benchmark');

const suite = new Benchmark.Suite();

suite

.add('Object.assign', function() {
  const a = {};
  const b = { a: 1, b: 2, c: 3, d: 4, e: 5};
  Object.assign(a, b);
})
.add('for in', function() {
  const a = {};
  const b = { a: 1, b: 2, c: 3, d: 4, e: 5};
  for (let key in b) {
    a[key] = b[key];
  }
})
.add('Object.keys', function() {
  const a = {};
  const b = { a: 1, b: 2, c: 3, d: 4, e: 5};
  const keys = Object.keys(b);
  for (var i = 0; i < keys.length; i++) {
    const key = keys[i];
    a[key] = b[key];
  }
})
.add('of Object.keys', function() {
  const a = {};
  const b = { a: 1, b: 2, c: 3, d: 4, e: 5};
  const keys = Object.keys(b);
  for (const key of keys) {
    a[key] = b[key];
  }
})
.on('cycle', function (event) {
  benchmarks.add(event.target);
})
.on('start', function () {
  console.log('\n  node version: %s, date: %s\n  Starting...', process.version, Date());
})
.on('complete', function() {
  benchmarks.log();
  process.exit(0);
})
.run({ 'async': false });

  // node version: v4.4.2, date: Fri Apr 29 2016 11:09:34 GMT+0800 (CST)
  // Starting...
  // 4 tests completed.

  // Object.assign      x   637,618 ops/sec ±1.59% (87 runs sampled)
  // for in             x 2,576,420 ops/sec ±1.21% (90 runs sampled)
  // Object.keys        x 3,087,945 ops/sec ±1.46% (86 runs sampled)
  // of Object.keys     x   874,902 ops/sec ±2.71% (86 runs sampled)