vue源码中数组方法重写实现逻辑？

Question

/*
 * not type checking this file because flow doesn't play well with
 * dynamically accessing methods on Array prototype
 */

import { def } from '../util/index'

const arrayProto = Array.prototype
export const arrayMethods = Object.create(arrayProto)

const methodsToPatch = [
  'push',
  'pop',
  'shift',
  'unshift',
  'splice',
  'sort',
  'reverse'
]

/**
 * Intercept mutating methods and emit events
 */
methodsToPatch.forEach(function (method) {
  // cache original method
  const original = arrayProto[method]
  def(arrayMethods, method, function mutator (...args) {
    const result = original.apply(this, args)
    const ob = this.__ob__
    let inserted
    switch (method) {
      case 'push':
      case 'unshift':
        inserted = args
        break
      case 'splice':
        inserted = args.slice(2)
        break
    }
    if (inserted) ob.observeArray(inserted)
    // notify change
    ob.dep.notify()
    return result
  })
})

vue源码中对原生数组方法重写，请问下为什么const result = original.apply(this, args)这段代码就可以达到监听数组变化的效果？求指教，谢谢！！！

Answer 1

const result = original.apply(this, args)这行不是监听，这个的作用是调用原来的原型上的数组方法,因为def重写了数组原型方法，那么你需要还原原来的行为，比如push操作就应该把数据推入进数组里，apply就是借用上面取出的原方法应用，因为你不能调用现在的push，会死循环