#apply 与 call 与 bind

const person = {
  firstName: 'John',
  lastName: 'Doe',
  fullName: function (param) {
    return `${param},${this.firstName} ${this.lastName}`
  },
}

const anotherPerson = {
  firstName: 'Jane',
  lastName: 'Doe',
}

console.log(person.fullName.apply(anotherPerson, ['hi'])) // 输出 "hi,Jane Doe"

Function.prototype.myApply = function (thisArg = globalThis, argArray) {
  // globalThis是全局的this指向如window/global/undefined

  // 唯一key防止覆盖
  const key = Symbol('key')

  // 调用apply的函数
  const fn = this

  // 绑定 fn 到thisArg
  thisArg[key] = fn

  // 使用thisArg 调用fn 并传参
  // 这里使用?.[]语法方便辨认是对象方法的调用，这样就改变了fn的this指向thisArg
  const res = thisArg?.[key](...argArray)

  // 删除绑定
  delete thisArg[key]

  return res
}

const person = {
  firstName: 'John',
  lastName: 'Doe',
  fullName: function (param) {
    return `${param},${this.firstName} ${this.lastName}`
  },
}

const anotherPerson = {
  firstName: 'Jane',
  lastName: 'Doe',
}

console.log(person.fullName.call(anotherPerson, 'hi')) // 输出 "hi,Jane Doe"

Function.prototype.myCall = function (thisArg = globalThis, ...argArray) {
  // globalThis是全局的this指向如window/global/undefined

  // 唯一key防止覆盖
  const key = Symbol('key')

  // 调用apply的函数
  const fn = this

  // 绑定 fn 到thisArg
  thisArg[key] = fn

  // 使用thisArg 调用fn 并传参
  // 这里使用?.[]语法方便辨认是对象方法的调用，这样就改变了fn的this指向thisArg
  const res = thisArg?.[key](...argArray)

  // 删除绑定
  delete thisArg[key]

  return res
}

Function.prototype.myBind = function (thisArg = globalThis, ...argArray) {
  // 不使用call实现会比较麻烦
  return (...args) => this.call(thisArg, ...argArray, ...args)
}