Run results for: Object for...in vs for...index with prototype 2

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_7 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/26.1 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 26

Operating system: iOS 18.7

Device Platform: Mobile

Date tested: 9 months ago

Test name	Executions per second
✓ forIndex	63,129 Ops/sec
forIn	20,783 Ops/sec

Script Preparation code:

// 生成测试对象
const createTestObject = (size) => {
  // 父对象（原型）
  const parent = {
    parentProp1: 'parent',
    parentProp2: 'parent2',
    parentProp3: {},
    parentProp4: [],
    parentMethod1() {
      return 'parentMethod';
    },
     parentMethod2() {
      return 'parentMethod';
    },
     parentMethod3() {
      return 'parentMethod';
    },
  };

  // 子对象（继承 Parent）
  const child = Object.create(parent);
  
  for (let i = 0; i < size; i++) {
    child[`key${i}`] = i;
  }
  return child;
};

// 测试 for...in
function testForIn(obj) {
  const start = performance.now();
  for (const key in obj) {
    if (Object.hasOwn(obj, key)) {
      const value = obj[key];
    }
  }
  return performance.now() - start;
}

// 测试 Object.keys + for
function testObjectKeysFor(obj) {
  const start = performance.now();
  const keys = Object.keys(obj);
  for (let i = 0; i < keys.length; i++) {
    const key = keys[i];
    const value = obj[key];
  }
  return performance.now() - start;
}

// 运行测试
const obj = createTestObject(1e3);

Run results for: Object for...in vs for...index with prototype 2

forIn

forIndex