15、webpack与tapable

事件驱动型事件流工作机制

负责创建bundles的compilation

tapable本身就是一个独立的库

实例化hook注册时间监听

通过hook出发事件监听

执行懒编译

hook本质就是tapable实例对象

hook执行机制分为同步和异步

Hook执行特点:

普通钩子:监听器之间互相不干扰

bailhook:熔断钩子,某个监听返回undefined时后续不执行

waterfallhook:瀑布钩子,上一个监听返回值可以传给下一个

loophook:循环钩子,当前监听未返回false则一直执行

上述都有同步钩子,例如SyncHook

AsyncSeriesHook

异步串行钩子

异步并行钩子

16、同步钩子的使用


const { SyncHook } = require('tapable')



let hook = new SyncHook(['name', 'age'])



hook.tap('fn1', function (name, age) {

console.log('fn1--->', name, age)

})


hook.tap('fn2', function (name, age) {

console.log('fn2--->', name, age)

})


hook.call('zoe', 18)//通过call方法调用





const { SyncBailHook } = require('tapable')



let hook = new SyncBailHook(['name', 'age'])



hook.tap('fn1', function (name, age) {

console.log('fn1--->', name, age)

})


hook.tap('fn2', function (name, age) {

console.log('fn2--->', name, age)

return undefined

})//返回undefined,fn3就不执行了


hook.tap('fn3', function (name, age) {

console.log('fn3--->', name, age)

})


hook.call('lg', 100)



const { SyncWaterfallHook } = require('tapable')



let hook = new SyncWaterfallHook(['name', 'age'])



hook.tap('fn1', function (name, age) {

console.log('fn1--->', name, age)

return 'ret1'

})


hook.tap('fn2', function (name, age) {
//这里的name拿到了ret1

console.log('fn2--->', name, age)

return 'ret2'

})


hook.tap('fn3', function (name, age) {

console.log('fn3--->', name, age)

return 'ret3'

})


hook.call('zce', 33)



const { SyncLoopHook } = require('tapable')



let hook = new SyncLoopHook(['name', 'age'])



let count1 = 0

let count2 = 0

let count3 = 0



hook.tap('fn1', function (name, age) {

console.log('fn1--->', name, age)

if (++count1 === 1) {

count1 = 0

return undefined//如果不返回undefined,就会从头再循环一次

}
return true

})


hook.tap('fn2', function (name, age) {

console.log('fn2--->', name, age)

// if (++count2 === 2) {
// count2 = 0
// return undefined
// }
// return true
})


hook.tap('fn3', function (name, age) {

console.log('fn3--->', name, age)

})


hook.call('foo', 100)

17、异步钩子


const { AsyncParallelHook } = require('tapable')

//并行是指 等待所有并发的异步事件执行之后再执行最终的异步回调

let hook = new AsyncParallelHook(['name'])



// 对于异步钩子的使用,在添加事件监听时会存在三种方式: tap tapAsync tapPromise
// hook.tap('fn1', function (name) {
// console.log('fn1--->', name)
// })


// hook.tap('fn2', function (name) {
// console.log('fn2--->', name)
// })


// hook.callAsync('zoe', function () {
// console.log('最后执行了回调操作')
// })


/* console.time('time')
hook.tapAsync('fn1', function (name, callback) {
setTimeout(() => {
console.log('fn1--->', name)
callback()
}, 1000)
})


hook.tapAsync('fn2', function (name, callback) {
setTimeout(() => {
console.log('fn2--->', name)
callback()
}, 2000)
})


hook.callAsync('lg', function () {
console.log('最后一个回调执行了')
console.timeEnd('time')
}) */


// 03 promise
console.time('time')
hook.tapPromise('fn1', function (name) {

return new Promise(function (resolve, reject) {

setTimeout(() => {

console.log('fn1--->', name)

resolve()
}, 1000)

})
})


hook.tapPromise('fn2', function (name) {

return new Promise(function (resolve, reject) {

setTimeout(() => {

console.log('fn2--->', name)

resolve()
}, 2000)

})
})


hook.promise('foo').then(() => {

console.log('end执行了')
console.timeEnd('time')
})

//最终输出:






const { AsyncParallelBailHook } = require('tapable')



let hook = new AsyncParallelBailHook(['name'])



console.time('time')
hook.tapAsync('fn1', function (name, callback) {

setTimeout(() => {

console.log('fn1--->', name)

callback()
}, 1000)

})


hook.tapAsync('fn2', function (name, callback) {

setTimeout(() => {

console.log('fn2--->', name)

callback('err’)//这边就会提前结束hook.callAsync的执行
}, 2000)

})


hook.tapAsync('fn3', function (name, callback) {

setTimeout(() => {

console.log('fn3--->', name)

callback()
}, 3000)

})


hook.callAsync('zce', function () {

console.log('最后的回调执行了')
console.timeEnd('time')
})


const { AsyncSeriesHook } = require('tapable')


//异步的串行
let hook = new AsyncSeriesHook(['name'])



console.time('time')
hook.tapPromise('fn1', function (name) {

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

setTimeout(() => {

console.log('fn1--->', name)

resolve()
}, 1000)

})
})


hook.tapPromise('fn2', function (name) {

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

setTimeout(() => {

console.log('fn2--->', name)

resolve()
}, 2000)

})
})


hook.promise('foo').then(function () {

console.log('~~~~')
console.timeEnd('time')
})

19、手写异步钩子

const SyncHook = require('./SyncHook.js')

let hook = new SyncHook(['name', 'age'])

hook.tap('fn1', function (name, age) {
console.log('fn1-->', name, age)
})

hook.tap('fn2', function (name, age) {
console.log('fn2-->', name, age)
})

hook.call('zoe66', 18)

/**

  • 01 实例化 hook , 定义 _x = [f1, f2, ...] taps = [{}, {}]
  • 02 实例调用 tap taps = [{}, {}]
  • 03 调用 call 方法, HookCodeFactory setup create
  • 04 Hook SyncHook HookCodeFactory
    */

let Hook = require('./Hook.js')


class HookCodeFactory {
  args() {
    return this.options.args.join(',')  // ["name", "age"]===> name, age
  }
  head() {
    return `var _x = this._x;`
  }
  content() {
    let code = ``
    for (var i = 0; i < this.options.taps.length; i++) {
      code += `var _fn${i} = _x[${i}];_fn${i}(${this.args()});`
    }
    return code
  }
  setup(instance, options) {  // 先准备后续需要使用到的数据
    this.options = options  // 这里的操作在源码中是通过 init 方法实现,而我们当前是直接挂在了 this 身上
    instance._x = options.taps.map(o => o.fn)   // this._x = [f1, f2, ....]
  }
  create() { // 核心就是创建一段可执行的代码体然后返回
    let fn
    // fn = new Function("name, age", "var _x = this._x, var _fn0 = _x[0]; _fn0(name, age);")
    // 在content中拼接出对应的代码片段
    fn = new Function(
      this.args(),
      this.head() + this.content()
    )
    return fn
  }
}


let factory = new HookCodeFactory()


class SyncHook extends Hook {
  constructor(args) {
    super(args)
  }


  compile(options) {  // {taps: [{}, {}], args: [name, age]}
    factory.setup(this, options)
    return factory.create(options)
  }
}


module.exports = SyncHook

./Hook.js

class Hook {
  constructor(args = []) {
    this.args = args
    this.taps = []  // 将来用于存放组装好的 {}对象信息
    this._x = undefined  // 将来在代码工厂函数中会给 _x = [f1, f2, f3....]
  }


  tap(options, fn) {
    if (typeof options === 'string') {
      options = { name: options }
    }
    options = Object.assign({ fn }, options)  // { fn:... name:fn1 }


    // 调用以下方法将组装好的 options 添加至this.taps
    this._insert(options)
  }


  _insert(options) {
    this.taps[this.taps.length] = options
  }


  call(...args) {
    // 01 创建将来要具体执行的函数代码结构
    let callFn = this._createCall()
    // 02 调用上述的函数(args传入进去)
    return callFn.apply(this, args)
  }


  _createCall() {
    return this.compile({
      taps: this.taps,
      args: this.args
    })
  }
}


module.exports = Hook

20、手写同步钩子


class Hook {
  constructor(args = []) {
    this.args = args
    this.taps = []  // 将来用于存放组装好的 {}
    this._x = undefined  // 将来在代码工厂函数中会给 _x = [f1, f2, f3....]
  }


  tap(options, fn) {
    if (typeof options === 'string') {
      options = { name: options }
    }
    options = Object.assign({ fn }, options)  // { fn:... name:fn1 }


    // 调用以下方法将组装好的 options 添加至 []
    this._insert(options)
  }


  tapAsync(options, fn) {
    if (typeof options === 'string') {
      options = { name: options }
    }
    options = Object.assign({ fn }, options)  // { fn:... name:fn1 }


    // 调用以下方法将组装好的 options 添加至 []
    this._insert(options)
  }


  _insert(options) {
    this.taps[this.taps.length] = options
  }


  call(...args) {
    // 01 创建将来要具体执行的函数代码结构
    let callFn = this._createCall()
    // 02 调用上述的函数(args传入进去)
    return callFn.apply(this, args)
  }


  callAsync(...args) {
    let callFn = this._createCall()
    return callFn.apply(this, args)
  }


  _createCall() {
    return this.compile({
      taps: this.taps,
      args: this.args
    })
  }
}


module.exports = Hook


let Hook = require('./Hook.js')


class HookCodeFactory {
  args({ after, before } = {}) {
    let allArgs = this.options.args
    if (before) allArgs = [before].concat(allArgs)
    if (after) allArgs = allArgs.concat(after)
    return allArgs.join(',')  // ["name", "age"]===> name, age
  }
  head() {
    return `"use strict";var _context;var _x = this._x;`
  }
  content() {
    let code = `var _counter = ${this.options.taps.length};var _done = (function () {
      _callback();
    });`
    for (var i = 0; i < this.options.taps.length; i++) {
      code += `var _fn${i} = _x[${i}];_fn${i}(name, age, (function () {
        if (--_counter === 0) _done();
      }));`
    }
    return code
  }
  setup(instance, options) {  // 先准备后续需要使用到的数据
    this.options = options  // 这里的操作在源码中是通过 init 方法实现,而我们当前是直接挂在了 this 身上
    instance._x = options.taps.map(o => o.fn)   // this._x = [f1, f2, ....]
  }
  create() { // 核心就是创建一段可执行的代码体然后返回
    let fn
    // fn = new Function("name, age", "var _x = this._x, var _fn0 = _x[0]; _fn0(name, age);")
    fn = new Function(
      this.args({ after: '_callback' }),
      this.head() + this.content()
    )
    return fn
  }
}


let factory = new HookCodeFactory()


class AsyncParallelHook extends Hook {
  constructor(args) {
    super(args)
  }


  compile(options) {  // {taps: [{}, {}], args: [name, age]}
    factory.setup(this, options)
    return factory.create(options)
  }
}


module.exports = AsyncParallelHook

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