Object

迭代

for...in

const obj = { a: 1, b: 2, c: 3 }

for (const key in obj) {
  // 过滤掉继承的属性
  if (obj.hasOwnProperty(key)) {
    console.log(`${key}: ${obj[key]}`)
  }
}

Object 方法

const obj = { a: 1, b: 2, c: 3 }

// Object.keys()
Object.keys(obj).forEach((key) => {
  console.log(`key: ${key}, value: ${obj[key]}`)
})

// Object.values()
Object.values(obj).forEach((value) => {
  console.log(`value: ${value}`)
})

// Object.entries()
Object.entries(obj).forEach(([key, value]) => {
  console.log(`key: ${key}, value: ${value}`)
})

for...of + Object.entries()

const obj = { a: 1, b: 2, c: 3 }

for (const [key, value] of Object.entries(obj)) {
  console.log(`key: ${key}, value: ${value}`)
}

size

const obj = { a: 1, b: 2, c: 3 }

const size = Object.keys(obj).length
console.log(size) // 3