JavaScript 手写方法

大厂手写题

1. 实现原生 AJAX 封装

const ajax = {
  get(url, fn) {
    const xhr = new XMLHttpRequest()
    xhr.open('GET', url, true)
    xhr.onreadystatechange = function() {
      if(xhr.readyState === 4) {
        fn(xhr.responseText)
      }
    }
    xhr.send()
  },
  post(url, fn, data) {
    const xhr = new XMLHttpRequest()
    xhr.open('POST', url, true)
    xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded')
    xhr.onreadystatechange = function() {
      if(xhr.readyState === 4) {
        fn(xhr.responseText)
      }
    }
    xhr.send(data)
  }
}

2. 实现 new 过程

function myNew(fn, ...args) {
    const obj = {}

    obj.__proto__ = fn.prototype

    fn.apply(obj, args)

    return obj
}

3. 打乱一个数组

// 方法1
const shuffle = (arr) => {
  return arr.sort(() => {
    return Math.random() > 0.5 ? 1 : -1
  })
}

// 方法2
const shuffle = (arr) => {
    let i = arr.length
    while (i) {
        let j = Math.floor(Math.random() * i--)
        [arr[j], arr[i]] = [arr[i], arr[j]]
    }
}

4. 防抖函数

function debounce(fn, delay = 200) {
  let timer
  return function(...args) {
    if (timer) {
      clearTimeout(timer)
      timer = null
    }
    timer = setTimeout(() => {
      fn.apply(this, args)
      clearTimeout(timer)
      timer = null
    }, delay)
  }
}

5. 节流函数

function throttle(fn, delay = 200) {
  let flag = true
  return function(...args) {
    if(!flag) {
      return
    }
    flag = false
    let timer = setTimeout(() => {
      fn.apply(this, args)
      flag = true
      clearTimeout(timer)
    }, delay)
  }
}

6. 数组去重

// 方法1
const quchong = (arr) => {
  return [...new Set(arr)]
}

// 方法2
const quchong = (arr) => {
  const res = []
  arr.reduce((pre, next) => {
    if (!pre.has(next)) {
      pre.set(next, 1)
      res.push(next)
    }
    return pre
  }, new Map())

  return res
}

7. setTimeout 实现 setInterval

const mySetInterval = (fn, delay) => {
  let timer = null
  const interval = () => {
    fn()
    timer = setTimeout(interval, delay)
  }
  timer = setTimeout(interval, delay)

  return {
    cancel: () => {
      clearTimeout(timer)
    }
  }
}

8. setInterval 实现 setTimeout

const mySetTimeout = (fn, delay) => {
  const timer = setInterval(() => {
    fn()
    clearInterval(timer)
  }, delay)
}

9. compose 函数

function fn1(x) {
  return x + 1;
}

function fn2(x) {
  return x + 2;
}

function fn3(x) {
  return x + 3;
}

function fn4(x) {
  return x + 4;
}
const compose = (...fns) => {
  if (fns.length === 0) return (num) => num
  if (fns.length === 1) return fns[0]
  return fns.reduce((pre, next) => {
    return (num) => {
      return pre(next(num))
    }
  })
}
const a = compose(fn1, fn2, fn3, fn4)
console.log(a(1)); // 1+2+3+4=11

10. curring 函数

const add = (a, b, c) => a + b + c;
const currying = (fn, ...args) => {
  let allArgs = [...args]
  const num = fn.length
  const res = (...args2) => {
    allArgs = [...allArgs, ...args2]
    if (allArgs.length === num) {
      return fn(...allArgs)
    } else {
      return res
    }
  }
  return res
}
const a = currying(add, 1);
console.log(a(2)(3)) // 1 + 2 + 3=6

11. LRU 算法

class LRUCache {
  constructor(size) {
    this.size = size
    this.cache = new Map()
  }
  get(key) {
    const hasKey = this.cache.has(key)
    if (!hasKey) {
      return -1
    } else {
      const val = this.cache.get(key)
      this.cache.delete(key)
      this.cache.set(key, val)
      return val
    }
  }
  put(key, value) {
    const hasKey = this.cache.has(key)
    if (hasKey) {
      this.cache.delete(key)
    }
    this.cache.set(key, value)
    if (this.cache.size > this.size) {
      this.cache.delete(this.cache.keys().next().value)
    }
  }
}

12. 发布订阅模式

class EventEmitter {
  constructor() {
    this.cache = []
  }

  on(name, fn) {
    const tasks = this.cache[name]
    if (tasks) {
      tasks.push(fn)
    } else {
      this.cache[name] = [fn]
    }
  }

  off(name, fn) {
    if (!name) {
      this.cache = []
      return
    }
    const tasks = this.cache[name]
    if (tasks) {
      if (!fn) {
        this.cache[name] = []
      }
      const index = tasks.findIndex(item => item === fn)
      if (index >= 0) {
        tasks.splice(index, 1)
      }
    }
  }

  emit(name, ...args) {
    // 复制一份。防止回调里继续on，导致死循环
    const tasks = this.cache[name].slice()
    if (tasks) {
      for (let task of tasks) {
        task(...args)
      }
    }
  }

  once(name, cb) {
    const fn = (...args) => {
      cb(...args)
      this.off(name, fn)
    }
    this.on(name, fn)
  }
}

13. DOM 转对象

const dom2tree = (node) => {
  const obj = {}
  obj.tag = node.tagName
  obj.children = []
  node.childNodes.forEach(child => obj.children.push(dom2tree(child)))
  return obj
}

14. 对象转 DOM

function _render(vnode) {
  if (typeof vnode === 'number') {
    vnode = String(vnode)
  }

  if (typeof vnode === 'string') {
    return document.createTextNode(vnode)
  }

  const dom = document.createElement(vnode.tag)
  if (vnode.attrs) {
    Object.keys(attrs).forEach(key => {
      const attr = artts[key]
      dom.setAttribute(key, attr)
    })
  }
  vnode.children.forEach(child => dom.appenChild(_render(child)))

  return dom
}

15. 判断对象环引用

const cycleDetector = (obj) => {
  const arr = [obj]
  let flag = false

  const cycle = (o) => {
    const values = Object.values(o)
    for (let value of values) {
      if (typeof value === 'object' && value !== null) {
        if (arr.includes(value)) {
          flag = true
          return
        }
        arr.push(value)
        cycle(value)
      }
    }
  }

  cycle(obj)

  return flag
}

16. 计算对象的层数

const loopGetLevel = (obj) => {
  let num = 1

  const computed = (obj, level) => {
    level = level || 0
    if (typeof obj === 'object' && obj !== null) {
      Object.values(obj).forEach(v => {
        if (typeof v === 'object' && v !== null) {
          computed(v, level + 1)
        } else {
          num = level + 1 > num ? level + 1 : num
        }
      })
    } else {
      num = level > num ? level : num
    }
  }
  computed(obj)

  return num
}

17. 对象的扁平化

const flatten = obj => {
  if (!isObject(obj)) return
  const res = {}
  const dfs = (cur, prefix) => {
    if (isObject(cur)) {
      if (Array.isArray(cur)) {
        for(let i in cur) {
          dfs(cur[i], `${prefix}[${i}]`)
        }
      } else {
        for(let i in cur) {
          dfs(cur[i], `${prefix}${prefix ? '.' : ''}${i}`)
        }
      }
    } else {
      res[prefix] = cur
    }
  }
  dfs(obj, '')

  return res
}

18. (a == 1 && a == 2 && a == 3)

// 第一种方法
var a = {
  i: 1,
  toString: function () {
    return a.i++;
  }
}
console.log(a == 1 && a == 2 && a == 3) // true

// 第二种方法
var a = [1, 2, 3];
a.join = a.shift;
console.log(a == 1 && a == 2 && a == 3); // true

// 第三种方法
var val = 0;
Object.defineProperty(window, 'a', {
    get: function () {
        return ++val;
    }
});
console.log(a == 1 && a == 2 && a == 3) // true

19. Promise 并发器

题目描述：

JS 实现一个带并发限制的异步调度器 Scheduler，保证同时运行的任务最多有两个

addTask(1000,"1");
addTask(500,"2");
addTask(300,"3");
addTask(400,"4");
的输出顺序是：2 3 1 4

整个的完整执行流程：

一开始1. 2两个任务开始执行
500ms时，2任务执行完毕，输出2，任务3开始执行
800ms时，3任务执行完毕，输出3，任务4开始执行
1000ms时，1任务执行完毕，输出1，此时只剩下4任务在执行
1200ms时，4任务执行完毕，输出4

实现：

class Scheduler {
  constructor(limit) {
    this.limit = limit
    this.queue = []
    this.count = 0
  }
  add(time, str) {
    const request = () => {
      return new Promise(resolve => {
        setTimeout(() => {
          console.log(str)
          resolve()
        }, time)
      })
    }
    this.queue.push(request)
  }
  taskStart() {
    for(let i = 0; i < this.limit; i++) {
      this.request()
    }
  }

  request() {
    if (!this.queue.length || this.count > this.limit) {
      return
    }
    this.count++
    this.queue.shift()().then(() => {
      this.count--
      this.request()
    })
  }
}

20. lazyMan 函数

要求：

实现一个LazyMan，可以按照以下方式调用:
LazyMan(“Hank”)输出:
Hi! This is Hank!

LazyMan(“Hank”).sleep(10).eat(“dinner”)输出
Hi! This is Hank!
//等待10秒..
Wake up after 10
Eat dinner~

LazyMan(“Hank”).eat(“dinner”).eat(“supper”)输出
Hi This is Hank!
Eat dinner~
Eat supper~

LazyMan(“Hank”).eat(“supper”).sleepFirst(5)输出
//等待5秒
Wake up after 5
Hi This is Hank!
Eat supper

解题：

class _lazyMan {
  constructor(name) {
    const fn = () => {
      console.log(`Hi! This is ${name}`)
      this.next()
    }
    this.tasks = []
    this.tasks.push(fn)
    setTimeout(() => {
      this.next()
    })
  }
  next() {
    const task = this.tasks.shift()
    task && task()
  }
  sleep(delay) {
    this.sleepWrapper(delay)
    return this
  }
  sleepFirst(delay) {
    this.sleepWrapper(delay, true)
    return this
  }
  sleepWrapper(time, first) {
    const fn = () => {
      setTimeout(() => {
        console.log(`Wake up after ${time}`)
        this.next()
      }, time * 1000)
    }
    if (first) {
      this.tasks.unshift(fn)
    } else {
      this.tasks.push(fn)
    }
  }
  eat(food) {
    const fn = () => {
      console.log(`Eat ${food}`)
      this.next()
    }
    this.tasks.push(fn)
    return this
  }

}

const LazyMan = (name) => {
  return new _lazyMan(name)
}

21. add 函数

要求：实现一个 add 方法使计算结果能够满足如下预期：

add(1)(2)(3)()=6
add(1,2,3)(4)()=10

解题：

function add(...args1) {
  let allArgs = [...args1]

  const fn = (...args2) => {
    allArgs = [...args1, ...args2]

    return fn
  }

  fn.toString = function() {
    return allArgs.reduce((pre, next) => {
      return pre + next
    })
  }

  return fn
}

22. 深拷贝

const tagMap = {
  mapTag: '[object Map]',
  setTag: '[object Set]',
  arrayTag: '[object Array]',
  objectTag: '[object Object]',
  symbolTag: '[object Symbol]',
  regexpTag: '[object RegExp]'
}


const checkType = (target) => {
  return Object.prototype.toString.call(target)
}

const checkTemp = (target) => {
  const c = target.constructor
  return new c()
}

const cloneSymbol = (target) => {
  return Object(Symbol.prototype.valueOf.call(target))
}

const cloneReg = (target) => {
  const reFlags = /\w*$/
  const result = new target.constructor(target.source, reFlags.exec(target))
  result.lastIndex = target.lastIndex
  return result
}

const deepClone = (target, map = new Map()) => {

  const type = checkType(target)

  if (!Object.values(tagMap).includes(type)) {
    return target
  }

  if (type === tagMap.symbolTag) {
    return cloneSymbol(target)
  }
  if (type === tagMap.regexpTag) {
    return cloneReg(target)
  }

    const temp = checkTemp(target)

  if (map.get(target)) {
    return map.get(target)
  }

  map.set(target, temp)

  if (type === tagMap.setTag) {
    target.forEach(value => {
      temp.add(deepClone(value, map))
    })
  }

  if (type === tagMap.mapTag) {
    target.forEach((value, key) => {
      temp.set(key, deepClone(value, map))
    })
  }

  for (const key in target) {
    temp[key] = deepClone(target[key], map)
  }
  return temp
}

23. 计算 LocalStorage 总容量

let str = '0123456789'
let temp = ''
// 先做一个 10KB 的字符串
while (str.length !== 10240) {
  str = str + '0123456789'
}

// 先清空
localStorage.clear()

const computedTotal = () => {
  return new Promise((resolve) => {
    // 不断往 LocalStorage 中累积存储 10KB
    const timer = setInterval(() => {
      try {
        localStorage.setItem('temp', temp)
      } catch {
        // 报错说明超出最大存储
        resolve(temp.length / 1024 - 10)
        clearInterval(timer)
        // 统计完记得清空
        localStorage.clear()
      }
      temp += str
    }, 0)
  })
}

(async () => {
  const total = await computedTotal()
  console.log(`最大容量${total}KB`)
})()

24. 实现 async/await

const toAsync = (fn) => {
  return function() {
    const gen = fn.apply(this. arguments)

    return new Promise((resolve, reject) => {

      function go(key, arg) {
        let res
        try {
          res = gen[key](arg)
        } catch(e) {
          return reject(e)
        }

        const { value, done } = res
        if (done) {
          return resolve(value)
        } else {
          return Promise.resolve(value).then(val => {
            go('next', val)
          }).catch(err => {
            go('throw', err)
          })
        }
      }
      go('next')
    })
  }
}

数组方法

27. forEach

Array.prototype.sx_forEach = (cb) => {
    for (let i = 0; i < this.length; i++) {
        cb && cb(this[i], i, this)
    }
}

28. map

Array.prototype.sx_map = (cb) => {
    const res = []
    for (let i = 0; i < this.length; i++) {
        res[i] = cb && cb(this[i], i, this)
    }
    return res
}

29. filter

Array.prototype.sx_filter = function (cb) {
    const res = []
    for (let i = 0; i < this.length; i++) {
        cb && cb(this[i], i, this) && (res.push(this[i]))
    }
    return res
}

30. every

Array.prototype.sx_every = function (cb) {
    for (let i = 0; i < this.length; i++) {
        if (!cb && cb(this[i], i, this)) {
            return false
        }
    }
    return true
}

31. some

Array.prototype.sx_some = function (cb) {
    for (let i = 0; i < this.length; i++) {
        if (cb && cb(this[i], i, this)) {
            return true
        }
    }
    return false
}

32. reduce

Array.prototype.sx_reduce = function (cb, ...args) {
    let pre, start = 0
    if (args.length) {
        pre = args[0]
    } else {
        pre = this[0]
        start = 1
    }
    for (let i = start; i < this.length; i++) {
        pre = cb(pre, this[i], i, this)
    }
    return pre
}

33. findIndex

Array.prototype.sx_findIndex = function (cb) {
    for (let i = 0; i < this.length; i++) {
        if (cb && cb(this[i], i, this)) {
            return i
        }
    }
    return -1
}

34. find

Array.prototype.sx_find = function (cb) {
    for (let i = 0; i < this.length; i++) {
        if (cb && cb(this[i], i, this)) {
            return this[i]
        }
    }
    return undefined
}

35. fill

Array.prototype.sx_fill = function (value, start = 0, end) {
    end = end || this.length
    for (let i = start; i < end; i++) {
        this[i] = value
    }
    return this
}

36. include

Array.prototype.sx_include = function (value, start = 0) {
    const isnan = Number.isNaN(value)
    for (let i = start; i < this.length; i++) {
        if (this[i] === value || (isnan && Number.isNaN(this[i]))) {
            return true
        }
    }
    return false
}

37. join

Array.prototype.sx_join = function (str = ',') {
    let resStr = ''
    for (let i = 0; i < this.length; i++) {
        const item = this[i]
        resStr = i === 0 ? item : `${resStr}${str}${item}`
    }
    return resStr
}

38. flat

Array.prototype.sx_flat = function (num = Infinity) {
    let arr = this, i = 0
    while (arr.some(item => Array.isArray(item))) {
        arr = [].concat(...arr)
        i++
        if (i >= num) break
    }
    return arr
}

39. splice

Array.prototype.sx_splice = function (start, length, ...values) {
    if (length === 0) return []
    length = start + length > this.length - 1 ? this.length - start : length
    console.log(length)
    const res = [], tempArr = [...this]
    for (let i = start; i < start + values.length; i++) {
        this[i] = values[i - start]
    }
    this.length = start + values.length
    if (values.length < length) {
        const cha = length - values.length
        for (let i = start + values.length; i < tempArr.length; i++) {
            this[i] = tempArr[i + cha]
        }
        this.length = this.length - cha
    }
    if (values.length > length) {
        for (let i = start + length; i < tempArr.length; i++) {
            this.push(tempArr[i])
        }
    }
    for (let i = start; i < start + length; i++) {
        res.push(tempArr[i])
    }
    return res
}

对象方法

40. entries

Object.prototype.sx_entries = function (obj) {
    const res = []
    for (let key in obj) {
        obj.hasOwnProperty(key) && (res.push([key, obj[key]]))
    }
    return res
}

41. fromEntries

Object.prototype.sx_fromEntries = function (arr) {
    const obj = {}
    for (let item of arr) {
        const [key, value] = item
        obj[key] = item[value]
    }
    return obj
}

42. keys

Object.prototype.sx_keys = function (obj) {
    const res = []
    for (let key in obj) {
        obj.hasOwnProperty(key) && res.push(key)
    }
    return res
}

43. values

Object.prototype.sx_values = function (obj) {
    const res = []
    for (let key in obj) {
        obj.hasOwnProperty(key) && res.push(obj[key])
    }
    return res
}

44. instanceOf

const instanceOf = function (parent, children) {
    const fp = parent.prototype
    let cp = children.__proto__
    while (cp) {
        if (fp === cp) {
            return true
        }
        cp = cp.__proto__
    }
    return false
}

45. is

Object.prototype.sx_is = function (x, y) {
    if (x === y) {
        // 防止 +0 和 -0
        return x !== 0 && 1 / x === 1 / y
    }

    // 防止NaN
    return x !== x && y !== y
}

46. assign

Object.prototype.sx_assign = function (target, ...args) {
    if (target === null || target === undefined) {
        throw new TypeError('Cannot convert undefined or null to object')
    }

    target = Object(target)

    for (let obj of args) {
        for (let key in obj) {
            obj.hasOwnProperty(key) && (target[key] = obj[key])
        }
    }

    return target
}

Promise 方法

47. all

Promise.sx_all = (promises) => {
    return new Promise((resolve, reject) => {
        const result = []
        let count = 0
        for (let i = 0; i < promises.length; i++) {
            const promise = Promise.resolve(promises[i])
            promise.then(res => {
                result[i] = res
                count++
                if (count === promises.length) {
                    resolve(result)
                }
            }).catch(err => {
                reject(err)
            })
        }
    })
}

48. race

Promise.sx_race = (promises) => {
    return new Promise((resolve, reject) => {
        for (let i = 0; i < promises.length; i++) {
            const promise = Promise.resolve(promises[i])
            promise.then(res => {
                resolve(res)
            }).catch(err => {
                reject(err)
            })
        }
    })
}

49. allSettled

Promise.sx_allSettled = (promises) => {
    return new Promise((resolve) => {
        const result = []
        let count = 0
        const addData = (status, value, i) => {
            result[i] = {
                status,
                value
            }
            count++
            if (count === promises.length) {
                resolve(result)
            }
        }
        for (let i = 0; i < promises.length; i++) {
            const promise = Promise.resolve(promises[i])
            promise.then(res => {
                addData('fulfilled', res, i)
            }).catch(err => {
                addData('rejected', err, i)
            })
        }
    })
}

50. any

Promise.sx_any = (promises) => {
    return new Promise((resolve, reject) => {
        let count = 0
        for (let i = 0; i < promises.length; i++) {
            const promise = Promise.resolve(promises[i])
            promise.then(res => {
                resolve(res)
            }).catch(err => {
                count++
                if (count === promises.length) {
                    reject('全错！！！')
                }
            })
        }
    })
}

51. finally

Promise.prototype.sx_finally = function (fn) {
  return this.then((res) => {
    fn()
    return res
  }).catch((err) => {
    fn()
    return err
  })
}

函数

52. call

Function.prototype.sx_call = function(obj, ...args) {
  obj = obj || window
  const fn = Symbol()
  obj[fn] = this
  const res = obj[fn](...args)
  delete obj[fn]
  return res
}

53. apply

Function.prototype.sx_apply = function(obj, args) {
  obj = obj || window
  const fn = Symbol()
  obj[fn] = this
  const res = obj[fn](...args)
  delete obj[fn]
  return res
}

54. bind

Function.prototype.sx_bind = function(obj, ...args) {
  obj = obj || window
  const fn = Symbol()
  obj[fn] = this
  const _this = this

  const res = function(...innerArgs) {
    console.log(this, _this)
    if (this instanceof _this) {
      this[fn] = _this
      this[fn](...[...args, ...innerArgs])
      delete this[fn]
    } else {
      obj[fn](...[...args, ...innerArgs])
      delete obj[fn]
    }
  }
  res.prototype = Object.create(this.prototype)
  return res
}

字符串

55. slice

String.prototype.sx_slice = function (start = 0, end) {
    start = start < 0 ? this.length + start : start
    end = !end && end !== 0 ? this.length : end

    if (start >= end) return ''
    let str = ''
    for (let i = start; i < end; i++) {
        str += this[i]
    }

    return str
}

56. substr

String.prototype.sx_substr = function (start = 0, length) {
    if (length < 0) return ''

    start = start < 0 ? this.length + start : start
    length = (!length && length !== 0) || length > this.length - start ? this.length : start + length

    let str = ''
    for (let i = start; i < length; i++) {
        str += this[i]
    }
    return str
}

57. substring

String.prototype.sx_sunstring = function (start = 0, end) {
    start = start < 0 ? this.length + start : start
    end = !end && end !== 0 ? this.length : end

    if (start >= end) [start, end] = [end, start]
    let str = ''
    for (let i = start; i < end; i++) {
        str += this[i]
    }

    return str
}

JavaScript 手写方法 ​

大厂手写题 ​

1. 实现原生 AJAX 封装 ​

2. 实现 new 过程 ​

3. 打乱一个数组 ​

4. 防抖函数 ​

5. 节流函数 ​

6. 数组去重 ​

7. setTimeout 实现 setInterval ​

8. setInterval 实现 setTimeout ​

9. compose 函数 ​

10. curring 函数 ​

11. LRU 算法 ​

12. 发布订阅模式 ​

13. DOM 转 对象 ​

14. 对象 转 DOM ​

15. 判断对象环引用 ​

16. 计算对象的层数 ​

17. 对象的扁平化 ​

18. (a == 1 && a == 2 && a == 3) ​

19. Promise 并发器 ​

20. lazyMan 函数 ​

21. add 函数 ​

22. 深拷贝 ​

23. 计算 LocalStorage 总容量 ​

24. 实现 async/await ​

数组方法 ​

27. forEach ​

28. map ​

29. filter ​

30. every ​

31. some ​

32. reduce ​

33. findIndex ​

34. find ​

35. fill ​

36. include ​

37. join ​

38. flat ​

39. splice ​

对象方法 ​

40. entries ​

41. fromEntries ​

42. keys ​

43. values ​

44. instanceOf ​

45. is ​

46. assign ​

Promise 方法 ​

47. all ​

48. race ​

49. allSettled ​

50. any ​

51. finally ​

函数 ​

52. call ​

53. apply ​

54. bind ​

字符串 ​

55. slice ​

56. substr ​

57. substring ​

JavaScript 手写方法

大厂手写题

1. 实现原生 AJAX 封装

2. 实现 new 过程

3. 打乱一个数组

4. 防抖函数

5. 节流函数

6. 数组去重

7. setTimeout 实现 setInterval

8. setInterval 实现 setTimeout

9. compose 函数

10. curring 函数

11. LRU 算法

12. 发布订阅模式

13. DOM 转对象

14. 对象转 DOM

15. 判断对象环引用

16. 计算对象的层数

17. 对象的扁平化

18. (a == 1 && a == 2 && a == 3)

19. Promise 并发器

20. lazyMan 函数

21. add 函数

22. 深拷贝

23. 计算 LocalStorage 总容量

24. 实现 async/await

数组方法

27. forEach

28. map

29. filter

30. every

31. some

32. reduce

33. findIndex

34. find

35. fill

36. include

37. join

38. flat

39. splice

对象方法

40. entries

41. fromEntries

42. keys

43. values

44. instanceOf

45. is

46. assign

Promise 方法

47. all

48. race

49. allSettled

50. any

51. finally

函数

52. call

53. apply

54. bind

字符串

55. slice

56. substr

57. substring