[JS] Object, Arrayループの実行速度比較

実行環境

CPU: Apple M1
OS: macOS 13.4.1
Node.js: v20.6.1
Memory: 8GB
Storage: 256GB

Object

実装方法

1. for in

for (const key in obj)

2. Object.keys (for of)

for (const key of Object.keys(obj))

3. Object.keys (forEach)

Object.keys(obj).forEach((key) => {});

4. Object.entries (for of)

for (const [key, value] of Object.entries(obj))

5. Object.entries (forEach)

Object.entries(obj).forEach(([key, value]) => {});

計測方法
N個のkeyを持つオブジェクトをループする操作を100,000回繰り返すのにかかる時間Tを計測し、各実装方法でNとTの関係を考察する

ベンチマークのコード

const iters = 100_000;

const keys = 1;
const obj = {};
for (let i = 0; i < keys; i++) {
  obj[`key${i}`] = i;
}

console.time('for in');
for (let i = 0; i < iters; i++) {
  for (const key in obj) {
    obj[key] += 1;
  }
}
console.timeEnd('for in');

console.time('Object.keys (for of)');
for (let i = 0; i < iters; i++) {
  for (const key of Object.keys(obj)) {
    obj[key] += 1;
  }
}
console.timeEnd('Object.keys (for of)');

console.time('Object.keys (forEach)');
for (let i = 0; i < iters; i++) {
  Object.keys(obj).forEach((key) => {
    obj[key] += 1;
  });
}
console.timeEnd('Object.keys (forEach)');

console.time('Object.entries (for of)');
for (let i = 0; i < iters; i++) {
  for (const [key, value] of Object.entries(obj)) {
    obj[key] += 1;
  }
}
console.timeEnd('Object.entries (for of)');

console.time('Object.entries (forEach)');
for (let i = 0; i < iters; i++) {
  Object.entries(obj).forEach(([key, value]) => {
    obj[key] += 1;
  });
}
console.timeEnd('Object.entries (forEach)');

結果

詳細な時間

Keyの数: 1

for in: 1.479ms
Object.keys (for of): 2.6ms
Object.keys (forEach): 1.805ms
Object.entries (for of): 4.592ms
Object.entries (forEach): 5.393ms

Keyの数: 10

for in: 1.923ms
Object.keys (for of): 3.655ms
Object.keys (forEach): 2.985ms
Object.entries (for of): 10.569ms
Object.entries (forEach): 10.512ms

Keyの数: 100

for in: 220.766ms
Object.keys (for of): 163.254ms
Object.keys (forEach): 160.879ms
Object.entries (for of): 1.073s
Object.entries (forEach): 1.135s

Keyの数: 1000

for in: 2.716s
Object.keys (for of): 1.819s
Object.keys (forEach): 1.830s
Object.entries (for of): 11.452s
Object.entries (forEach): 11.464s

Array

実装方法

1. for let

for (let j = 0; j < arr.length; j++)

2. for of

for (const item of arr)

3. for of .entries

for (const [index, item] of arr.entries())

4. for of .keys

for (const index of arr.keys())

5. forEach

arr.forEach((item, index) => {}))

計測方法
N個の要素を持つ配列をループする操作を100,000回繰り返すのにかかる時間Tを計測し、各実装方法でNとTの関係を考察する

結果

詳細な時間

要素数: 1

for let: 2.958ms
for of: 3.672ms
for of .entries: 9.126ms
for of .keys: 3.208ms
forEach: 3.523ms

要素数: 10

for let: 5.969ms
for of: 9.251ms
for of .entries: 53.897ms
for of .keys: 8.947ms
forEach: 7.245ms

要素数: 100

for let: 34.301ms
for of: 72.622ms
for of .entries: 513.946ms
for of .keys: 74.407ms
forEach: 35.735ms

要素数: 1000

for let: 326.696ms
for of: 640.936ms
for of .entries: 4.796s
for of .keys: 644.261ms
forEach: 340.525ms