关于javascript:webpack源码分析2

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15、webpack 与 tapable

事件驱动型事件流工作机制

负责创立 bundles 的 compilation

tapable 自身就是一个独立的库

实例化 hook 注册工夫监听

通过 hook 登程事件监听

执行懒编译

hook 实质就是 tapable 实例对象

hook 执行机制分为同步和异步

Hook 执行特点：

一般钩子：监听器之间相互不烦扰

bailhook：熔断钩子，某个监听返回 undefined 时后续不执行

waterfallhook：瀑布钩子，上一个监听返回值能够传给下一个

loophook：循环钩子，以后监听未返回 false 则始终执行

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、同步钩子的应用


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 办法调用





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 期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'])



// 对于异步钩子的应用，在增加事件监听时会存在三种形式：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('最初执行了回调操作')
// })


/* 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('最初一个回调执行了')
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')
})

// 最终输入：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('最初的回调执行了')
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 办法，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) {  // 先筹备后续须要应用到的数据
    this.options = options  // 这里的操作在源码中是通过 init 办法实现，而咱们以后是间接挂在了 this 身上
    instance._x = options.taps.map(o => o.fn)   // this._x = [f1, f2, ....]
  }
  create() { // 外围就是创立一段可执行的代码体而后返回
    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 = []  // 未来用于寄存组装好的 {} 对象信息
    this._x = undefined  // 未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}


    // 调用以下办法将组装好的 options 增加至 this.taps
    this._insert(options)
  }


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


  call(...args) {
    // 01 创立未来要具体执行的函数代码构造
    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 = []  // 未来用于寄存组装好的 {}
    this._x = undefined  // 未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}


    // 调用以下办法将组装好的 options 增加至 []
    this._insert(options)
  }


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


    // 调用以下办法将组装好的 options 增加至 []
    this._insert(options)
  }


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


  call(...args) {
    // 01 创立未来要具体执行的函数代码构造
    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) {  // 先筹备后续须要应用到的数据
    this.options = options  // 这里的操作在源码中是通过 init 办法实现，而咱们以后是间接挂在了 this 身上
    instance._x = options.taps.map(o => o.fn)   // this._x = [f1, f2, ....]
  }
  create() { // 外围就是创立一段可执行的代码体而后返回
    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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