Run results for: JavaScript spread operator vs Object.assign performance 22476

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 15_4_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.4 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 15

Operating system: iOS 15.4.1

Device Platform: Mobile

Date tested: 2 years ago

Test name	Executions per second
Using the spread operator	3229633.0 Ops/sec
Using Object.assign	2461295.0 Ops/sec
Babel	500511.8 Ops/sec

Script Preparation code:

const obj1 = { a: "a" };
const obj2 = { b: "b" };

function _defineProperty(obj, key, value) {
  if (key in obj) {
    Object.defineProperty(obj, key, {
      value: value,
      enumerable: true,
      configurable: true,
      writable: true
    });
  } else {
    obj[key] = value;
  }

  return obj;
}

function ownKeys(object, enumerableOnly) {
  var keys = Object.keys(object);

  if (Object.getOwnPropertySymbols) {
    var symbols = Object.getOwnPropertySymbols(object);
    if (enumerableOnly) symbols = symbols.filter(function (sym) {
      return Object.getOwnPropertyDescriptor(object, sym).enumerable;
    });
    keys.push.apply(keys, symbols);
  }

  return keys;
}

function _objectSpread2(target) {
  for (var i = 1; i < arguments.length; i++) {
    var source = arguments[i] != null ? arguments[i] : {};

    if (i % 2) {
      ownKeys(Object(source), true).forEach(function (key) {
        _defineProperty(target, key, source[key]);
      });
    } else if (Object.getOwnPropertyDescriptors) {
      Object.defineProperties(target, Object.getOwnPropertyDescriptors(source));
    } else {
      ownKeys(Object(source)).forEach(function (key) {
        Object.defineProperty(target, key, Object.getOwnPropertyDescriptor(source, key));
      });
    }
  }

  return target;
}

window.obj1 = obj1;
window.obj2 = obj2;
window._objectSpread2 = _objectSpread2;

Tests:

Using the spread operator
const finalObject = { c: "a", ...obj1, ...obj2 };
Using Object.assign
const finalObject = Object.assign({ c: "a" }, obj1, obj2);
Babel
_objectSpread2({ c: "a" }, obj1, obj2);

Run results for: JavaScript spread operator vs Object.assign performance 22476

Using the spread operator

Using Object.assign

Babel