跳到主要内容

循环

循环写法​

在 JavaScript 中，有多种循环语句可供选择，以满足不同的需求。以下是 JavaScript 中所有的循环写法：

1. for 循环：​

for (let i = 0; i < 5; i++) {
  console.log(i)
}

2. while 循环：​

let i = 0
while (i < 5) {
  console.log(i)
  i++
}

3. do...while 循环：​

let i = 0
do {
  console.log(i)
  i++
} while (i < 5)

4. for...in 循环（遍历对象的属性）：​

const person = {
  name: 'Alice',
  age: 25,
  gender: 'female',
}

for (let key in person) {
  console.log(key + ': ' + person[key])
}

5. for...of 循环（遍历可迭代对象）：​

const fruits = ['apple', 'orange', 'banana']
for (let fruit of fruits) {
  console.log(fruit)
}

6. Array.prototype.forEach() 方法：​

const fruits = ['apple', 'orange', 'banana']
fruits.forEach((fruit, index) => {
  console.log(fruit + ' at index ' + index)
})

7. Array.prototype.map() 方法：​

const numbers = [1, 2, 3, 4, 5]
const squareNumbers = numbers.map((number) => {
  return number * number
})
console.log(squareNumbers)

8. Array.prototype.filter() 方法：​

const numbers = [1, 2, 3, 4, 5]
const evenNumbers = numbers.filter((number) => {
  return number % 2 === 0
})
console.log(evenNumbers)

9. Array.prototype.reduce() 方法：​

const numbers = [1, 2, 3, 4, 5]
const sum = numbers.reduce((accumulator, currentValue) => {
  return accumulator + currentValue
}, 0)
console.log(sum)

10. Array.prototype.every() 方法：​

const numbers = [1, 2, 3, 4, 5]
const allPositive = numbers.every((number) => {
  return number > 0
})
console.log(allPositive)

11. Array.prototype.some() 方法：​

const numbers = [1, 2, 3, 4, -5]
const hasNegative = numbers.some((number) => {
  return number < 0
})
console.log(hasNegative)

12. Iterator 迭代器：​

const colors = ['red', 'green', 'blue']
const iterator = colors[Symbol.iterator]()
let next = iterator.next()
while (!next.done) {
  console.log(next.value)
  next = iterator.next()
}

13. for...await...of 循环（用于异步迭代）：​

const asyncFunc = async () => {
  const promises = [Promise.resolve(1), Promise.resolve(2), Promise.resolve(3)]
  for await (const result of promises) {
    console.log(result)
  }
}
asyncFunc()

14. generator 函数配合 for...of 循环：​

function* generatorFunction() {
  yield 1
  yield 2
  yield 3
}

const generator = generatorFunction()
for (const value of generator) {
  console.log(value)
}

15. Object.entries() 配合 for...of 循环（遍历对象的键值对）：​

const person = {
  name: 'Alice',
  age: 25,
  gender: 'female',
}

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

16. Object.keys() 配合 forEach() 方法（遍历对象的键）：​

const person = {
  name: 'Alice',
  age: 25,
  gender: 'female',
}

Object.keys(person).forEach((key) => {
  console.log(key)
})