面向切面实现

/**
* 执行之前
**/
Function.prototype.before = function (beforeFn) {
  let _self = this
  return function() {
    beforeFn.apply(this, arguments)
    return _self.apply(this, arguments)
  }
}

/**
* 执行之后
**/
Function.prototype.after = function (afterFn) {
  let _self = this
  return function() {
    let after = _self.apply(this, arguments)
    afterFn.apply(this, arguments)
    return after
  }
}

let f = function(){
  console.log(1)
}

let a = function a () {
  console.log(0)
}

let b = function b () {
  console.log(2)
}

f = f.before(a).after(b)
f()

js钩子实例.png