Micro-benchmark to measure the performance different of Object.assign() vs. object spread

bench-object-spread-vs-object-assign.js

// Copyright 2013-2019 Benedikt Meurer
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     <https://www.apache.org/licenses/LICENSE-2.0>
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

if (typeof console === 'undefined') console = {log:print};

var INPUT = {
    "_id": "5c49a3f586a314e1da9bc5c4",
    "index": 0,
    "guid": "4a19223f-e806-4590-b0b2-bc52854010e9",
    "isActive": true,
    "balance": "$1,341.65",
    "picture": "http://placehold.it/32x32",
    "age": 33,
    "eyeColor": "brown",
    "name": "English Peck",
    "gender": "male",
    "company": "APPLIDECK",
    "email": "englishpeck@applideck.com",
    "phone": "+1 (995) 574-3187",
    "address": "479 Lloyd Court, Cecilia, District Of Columbia, 4378",
    "about": "Sunt laborum commodo ex nisi. Sint amet sit excepteur qui do veniam qui sint sit labore id. Laboris laborum amet eiusmod laborum duis.\r\n",
    "registered": "2017-02-11T03:09:56 -01:00",
    "latitude": 31.939115,
    "longitude": -54.305863,
    "tags": [
      "laborum",
      "laboris",
      "cupidatat",
      "nostrud",
      "dolore",
      "ex",
      "duis"
    ],
    "friends": [
      {
              "id": 0,
              "name": "Susie Sawyer"
            },
      {
              "id": 1,
              "name": "Lola Ware"
            },
      {
              "id": 2,
              "name": "Bender Barrera"
            }
    ],
    "greeting": "Hello, English Peck! You have 10 unread messages.",
    "favoriteFruit": "banana"
  };

const TESTS = [];
const N = 1e6;

(function() {
  TESTS.push(
      function objectSpreadFirst(input) {
        return {...input, x: 1};
      },
      function objectAssignFirst(input) {
        return Object.assign({}, input, {x:1});
      },
      function objectSpreadLast(input) {
        return {x: 1, ...input};
      },
      function objectAssignLast(input) {
        return Object.assign({}, {x:1}, input);
      }
  );
})();

function test(fn) {
  var result;
  for (var i = 0; i < N; ++i) {
    result = fn(INPUT);
  }
  return result;
}
test(x => x);  // Pollute call feedback early on.

for (var j = 0; j < TESTS.length; ++j) {
  test(TESTS[j]);
}

for (var j = 0; j < TESTS.length; ++j) {
  var startTime = Date.now();
  test(TESTS[j]);
  console.log(`${TESTS[j].name}: ${Date.now() - startTime} ms.`);
}