vue源码（一）

搭建环境

获取地址：GitHub - vuejs/vue: This is the repo for Vue 2. For Vue 3, go to https://github.com/vuejs/core

安装依赖：npm i

安装 rollup：

npm i -g -rollup

修改dev脚本：添加 --sourcemap

"dev": "rollup -w -c scripts/config.js --sourcemap --environment TARGET:web-full-dev",

执行dev脚本：npm run dev

此处使用vue的版本是2.6

目录：

dist 发布目录 

examples 范例

flow 试代码 

node_modules

scripts 构建脚本

src 源码

  compiler 编译器相关

  core 核心代码

    components 通用组件如keep-alive

    global-api 全局api

    instance 构造函数等

    observer 响应式相关

    util 

    vdom 虚拟DOM相关

......

术语解释：

runtime 仅包含运行时，不包含编译器

common cjs规范，适用于webpack1

esm es模块，用于webpack2+

umd universal module definition，兼容cjs和amd，用于浏览器，一般使用的都是这个版本。

入口文件

-c scripts/config.js //配置文件所在

TARGET:web-full-dev" //指明输出文件配置项

能够通过config.js找到对应的entry入口文件

// Runtime+compiler development build (Browser)
  'web-full-dev': {
    entry: resolve('web/entry-runtime-with-compiler.js'),
    dest: resolve('dist/vue.js'),
    format: 'umd',
    env: 'development',
    alias: { he: './entity-decoder' },
    banner
  },

所以默认是web开头的路径

const aliases = require('./alias')
const resolve = p => {
  const base = p.split('/')[0]
  if (aliases[base]) {
    return path.resolve(aliases[base], p.slice(base.length + 1))
  } else {
    return path.resolve(__dirname, '../', p)
  }
}

进入alias

module.exports = {
  vue: resolve('src/platforms/web/entry-runtime-with-compiler'),
  compiler: resolve('src/compiler'),
  core: resolve('src/core'),
  shared: resolve('src/shared'),
  web: resolve('src/platforms/web'),
  weex: resolve('src/platforms/weex'),
  server: resolve('src/server'),
  sfc: resolve('src/sfc')
}

找到了最终的路径

/Users/jerrychen/Desktop/vue-2.6/src/platforms/web/entry-runtime-with-compiler.js

//扩展$mount:解析模版
const mount = Vue.prototype.$mount
Vue.prototype.$mount = function (
  el?: string | Element, //宿主元素
  hydrating?: boolean
): Component {
    el = el && query(el) //获取真实dom
    ......
}

 解析模版相关选项，首先判断是否有render函数，所以render的优先级很高，再看template，最后是el。如果写了el，则可以省略$mount。template或者render需要加上$mount。

//检测render函数
if (!options.render) {
    //再看template
    let template = options.template
    //解析template
    if (template) {
      if (typeof template === 'string') {  //template:'#app' 选择器
        if (template.charAt(0) === '#') {
          template = idToTemplate(template)
          /* istanbul ignore if */
          if (process.env.NODE_ENV !== 'production' && !template) {
            warn(
              `Template element not found or is empty: ${options.template}`,
              this
            )
          }
        }
      } else if (template.nodeType) { //dom节点
        template = template.innerHTML
      } else {
        if (process.env.NODE_ENV !== 'production') {
          warn('invalid template option:' + template, this)
        }
        return this
      }
    } else if (el) { //最后一种情况查看el选项
      template = getOuterHTML(el)
    }
    //如何处理模版，编译渲染
    if (template) {
      /* istanbul ignore if */
      if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
        mark('compile')
      }

      const { render, staticRenderFns } = compileToFunctions(template, {
        outputSourceRange: process.env.NODE_ENV !== 'production',
        shouldDecodeNewlines,
        shouldDecodeNewlinesForHref,
        delimiters: options.delimiters,
        comments: options.comments
      }, this)
      //重新赋值给我们的选项
      options.render = render
      options.staticRenderFns = staticRenderFns

      /* istanbul ignore if */
      if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
        mark('compile end')
        measure(`vue ${this._name} compile`, 'compile', 'compile end')
      }
    }
  }

Vue的路径

/Users/jerrychen/Desktop/vue-2.6/src/platforms/web/runtime/index.js

 安装平台patch函数，实现跨平台操作

实现$mount('#app')=>mountComponent 在内部render()=>vdom => patch()将虚拟dom转为真实dom=>dom，最后追加到宿主元素#app上。

// install platform patch function
//安装平台特有的补丁函数：用来做初始化和更新的
Vue.prototype.__patch__ = inBrowser ? patch : noop

// public mount method
//实现 $mount：初始化的挂载
Vue.prototype.$mount = function (
  el?: string | Element,
  hydrating?: boolean
): Component {
  el = el && inBrowser ? query(el) : undefined
  return mountComponent(this, el, hydrating)
}

---

 

/Users/jerrychen/Desktop/vue-2.6/src/core/index.js

初始化全局api，Vue.use/component/directive/filter/mixin/set/extend/delete等。

//初始化全局api
initGlobalAPI(Vue)

/Users/jerrychen/Desktop/vue-2.6/src/core/global-api/index.js

/* @flow */

import config from '../config'
import { initUse } from './use'
import { initMixin } from './mixin'
import { initExtend } from './extend'
import { initAssetRegisters } from './assets'
import { set, del } from '../observer/index'
import { ASSET_TYPES } from 'shared/constants'
import builtInComponents from '../components/index'
import { observe } from 'core/observer/index'

import {
  warn,
  extend,
  nextTick,
  mergeOptions,
  defineReactive
} from '../util/index'

export function initGlobalAPI (Vue: GlobalAPI) {
  // config
  const configDef = {}
  configDef.get = () => config
  if (process.env.NODE_ENV !== 'production') {
    configDef.set = () => {
      warn(
        'Do not replace the Vue.config object, set individual fields instead.'
      )
    }
  }
  Object.defineProperty(Vue, 'config', configDef)

  // exposed util methods.
  // NOTE: these are not considered part of the public API - avoid relying on
  // them unless you are aware of the risk.
  Vue.util = {
    warn,
    extend,
    mergeOptions,
    defineReactive
  }

  Vue.set = set
  Vue.delete = del
  Vue.nextTick = nextTick

  // 2.6 explicit observable API
  Vue.observable = (obj: T): T => {
    observe(obj)
    return obj
  }

  Vue.options = Object.create(null)
  ASSET_TYPES.forEach(type => {
    Vue.options[type + 's'] = Object.create(null)
  })

  // this is used to identify the "base" constructor to extend all plain-object
  // components with in Weex's multi-instance scenarios.
  Vue.options._base = Vue

  extend(Vue.options.components, builtInComponents)

  initUse(Vue)
  initMixin(Vue)
  initExtend(Vue)
  initAssetRegisters(Vue)
}

/* @flow */

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

export function initUse (Vue: GlobalAPI) {
  //Vue.use(VueRouter,options)
  Vue.use = function (plugin: Function | Object) {
    const installedPlugins = (this._installedPlugins || (this._installedPlugins = []))
    if (installedPlugins.indexOf(plugin) > -1) {
      return this
    }

    // additional parameters
    //[Vue,options]
    const args = toArray(arguments, 1)
    args.unshift(this)
    if (typeof plugin.install === 'function') {
      plugin.install.apply(plugin, args)
    } else if (typeof plugin === 'function') {
      plugin.apply(null, args)
    }
    installedPlugins.push(plugin)
    return this
  }
}

---

 vue构建函数，声明实例属性和方法， 初始化，initMIxin中混入了_init函数

/Users/jerrychen/Desktop/vue-2.6/src/core/instance/index.js

//构造函数：new Vue(options)
function Vue (options) {
  if (process.env.NODE_ENV !== 'production' &&
    !(this instanceof Vue)
  ) {
    warn('Vue is a constructor and should be called with the `new` keyword')
  }
  //初始化
  this._init(options)
}

initMixin(Vue) //提供_init方法
// 我们熟悉的其他实例属性和方法由下面这些混入
stateMixin(Vue)
eventsMixin(Vue)
lifecycleMixin(Vue)
renderMixin(Vue)

---

/Users/jerrychen/Desktop/vue-2.6/src/core/instance/init.js

//合并选项：new Vue时传入的是用户配置选项，他们要和系统配置合并
    if (options && options._isComponent) {
      // optimize internal component instantiation
      // since dynamic options merging is pretty slow, and none of the
      // internal component options needs special treatment.
      initInternalComponent(vm, options)
    } else {
      vm.$options = mergeOptions(
        resolveConstructorOptions(vm.constructor),
        options || {},
        vm
      )
    }
    /* istanbul ignore else */
    if (process.env.NODE_ENV !== 'production') {
      initProxy(vm)
    } else {
      vm._renderProxy = vm
    }
    // expose real self
    vm._self = vm
    initLifecycle(vm) //示例属性 $parent,$root,$chiltren $refs
    initEvents(vm) //自定义事件的处理
    initRender(vm) //插槽，createElement函数
    callHook(vm, 'beforeCreate')
    //组件状态相关的数据操作
    initInjections(vm) // resolve injections before data/props
    initState(vm) //数据响应式 props，methods data copmputed watch
    initProvide(vm) // resolve provide after data/props
    callHook(vm, 'created')

    /* istanbul ignore if */
    if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
      vm._name = formatComponentName(vm, false)
      mark(endTag)
      measure(`vue ${vm._name} init`, startTag, endTag)
    }
    //如果设置了el，则自动执行$mount()
    if (vm.$options.el) {
      vm.$mount(vm.$options.el)
    }

 $mount函数最终还是mountComponent函数

// /Users/jerrychen/Desktop/vue-2.6/src/platforms/web/runtime/index.js
//实现 $mount：初始化的挂载
Vue.prototype.$mount = function (
  el?: string | Element,
  hydrating?: boolean
): Component {
  el = el && inBrowser ? query(el) : undefined
  return mountComponent(this, el, hydrating)
}

export function mountComponent (
  vm: Component,
  el: ?Element,
  hydrating?: boolean
): Component {
  vm.$el = el
  if (!vm.$options.render) {
    vm.$options.render = createEmptyVNode
    if (process.env.NODE_ENV !== 'production') {
      /* istanbul ignore if */
      if ((vm.$options.template && vm.$options.template.charAt(0) !== '#') ||
        vm.$options.el || el) {
        warn(
          'You are using the runtime-only build of Vue where the template ' +
          'compiler is not available. Either pre-compile the templates into ' +
          'render functions, or use the compiler-included build.',
          vm
        )
      } else {
        warn(
          'Failed to mount component: template or render function not defined.',
          vm
        )
      }
    }
  }
  callHook(vm, 'beforeMount')

  let updateComponent
  /* istanbul ignore if */
  if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
    updateComponent = () => {
      const name = vm._name
      const id = vm._uid
      const startTag = `vue-perf-start:${id}`
      const endTag = `vue-perf-end:${id}`

      mark(startTag)
      const vnode = vm._render()
      mark(endTag)
      measure(`vue ${name} render`, startTag, endTag)

      mark(startTag)
      vm._update(vnode, hydrating)
      mark(endTag)
      measure(`vue ${name} patch`, startTag, endTag)
    }
  } else {
    updateComponent = () => {
      vm._update(vm._render(), hydrating)
    }
  }

  // we set this to vm._watcher inside the watcher's constructor
  // since the watcher's initial patch may call $forceUpdate (e.g. inside child
  // component's mounted hook), which relies on vm._watcher being already defined
  new Watcher(vm, updateComponent, noop, {
    before () {
      if (vm._isMounted && !vm._isDestroyed) {
        callHook(vm, 'beforeUpdate')
      }
    }
  }, true /* isRenderWatcher */)
  hydrating = false

  // manually mounted instance, call mounted on self
  // mounted is called for render-created child components in its inserted hook
  if (vm.$vnode == null) {
    vm._isMounted = true
    callHook(vm, 'mounted')
  }
  return vm
}

 会生成watcher并且调用updateComponent函数，传入render函数并调用，最后执行_update更新函数

// /Users/jerrychen/Desktop/vue-2.6/src/core/instance/lifecycle.js

export function mountComponent (
  vm: Component,
  el: ?Element,
  hydrating?: boolean
): Component {
  vm.$el = el
  if (!vm.$options.render) {
    vm.$options.render = createEmptyVNode
    if (process.env.NODE_ENV !== 'production') {
      /* istanbul ignore if */
      if ((vm.$options.template && vm.$options.template.charAt(0) !== '#') ||
        vm.$options.el || el) {
        warn(
          'You are using the runtime-only build of Vue where the template ' +
          'compiler is not available. Either pre-compile the templates into ' +
          'render functions, or use the compiler-included build.',
          vm
        )
      } else {
        warn(
          'Failed to mount component: template or render function not defined.',
          vm
        )
      }
    }
  }
  callHook(vm, 'beforeMount')

  let updateComponent
  /* istanbul ignore if */
  if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
    updateComponent = () => {
      const name = vm._name
      const id = vm._uid
      const startTag = `vue-perf-start:${id}`
      const endTag = `vue-perf-end:${id}`

      mark(startTag)
      const vnode = vm._render()
      mark(endTag)
      measure(`vue ${name} render`, startTag, endTag)

      mark(startTag)
      vm._update(vnode, hydrating)
      mark(endTag)
      measure(`vue ${name} patch`, startTag, endTag)
    }
  } else {
    updateComponent = () => {
      vm._update(vm._render(), hydrating)
    }
  }

  // we set this to vm._watcher inside the watcher's constructor
  // since the watcher's initial patch may call $forceUpdate (e.g. inside child
  // component's mounted hook), which relies on vm._watcher being already defined
  new Watcher(vm, updateComponent, noop, {
    before () {
      if (vm._isMounted && !vm._isDestroyed) {
        callHook(vm, 'beforeUpdate')
      }
    }
  }, true /* isRenderWatcher */)
  hydrating = false

  // manually mounted instance, call mounted on self
  // mounted is called for render-created child components in its inserted hook
  if (vm.$vnode == null) {
    vm._isMounted = true
    callHook(vm, 'mounted')
  }
  return vm
}

执行render函数得到虚拟dom

// /Users/jerrychen/Desktop/vue-2.6/src/core/instance/render.js
export function renderMixin (Vue: Class) {
  // install runtime convenience helpers
  installRenderHelpers(Vue.prototype)

  Vue.prototype.$nextTick = function (fn: Function) {
    return nextTick(fn, this)
  }

  Vue.prototype._render = function (): VNode {
    const vm: Component = this
    const { render, _parentVnode } = vm.$options

    if (_parentVnode) {
      vm.$scopedSlots = normalizeScopedSlots(
        _parentVnode.data.scopedSlots,
        vm.$slots,
        vm.$scopedSlots
      )
    }

    // set parent vnode. this allows render functions to have access
    // to the data on the placeholder node.
    vm.$vnode = _parentVnode
    // render self
    let vnode
    try {
      // There's no need to maintain a stack because all render fns are called
      // separately from one another. Nested component's render fns are called
      // when parent component is patched.
      currentRenderingInstance = vm
      vnode = render.call(vm._renderProxy, vm.$createElement)
    } catch (e) {
      handleError(e, vm, `render`)
      // return error render result,
      // or previous vnode to prevent render error causing blank component
      /* istanbul ignore else */
      if (process.env.NODE_ENV !== 'production' && vm.$options.renderError) {
        try {
          //执行渲染函数获得虚拟dom
          vnode = vm.$options.renderError.call(vm._renderProxy, vm.$createElement, e)
        } catch (e) {
          handleError(e, vm, `renderError`)
          vnode = vm._vnode
        }
      } else {
        vnode = vm._vnode
      }
    } finally {
      currentRenderingInstance = null
    }
    // if the returned array contains only a single node, allow it
    if (Array.isArray(vnode) && vnode.length === 1) {
      vnode = vnode[0]
    }
    // return empty vnode in case the render function errored out
    if (!(vnode instanceof VNode)) {
      if (process.env.NODE_ENV !== 'production' && Array.isArray(vnode)) {
        warn(
          'Multiple root nodes returned from render function. Render function ' +
          'should return a single root node.',
          vm
        )
      }
      vnode = createEmptyVNode()
    }
    // set parent
    vnode.parent = _parentVnode
    return vnode
  }
}

最后使用update更新函数进行更新 ，调用patch函数，既可以初始化也可以更新。

// /Users/jerrychen/Desktop/vue-2.6/src/core/instance/lifecycle.js
Vue.prototype._update = function (vnode: VNode, hydrating?: boolean) {
    const vm: Component = this
    const prevEl = vm.$el
    const prevVnode = vm._vnode
    const restoreActiveInstance = setActiveInstance(vm)
    vm._vnode = vnode
    // Vue.prototype.__patch__ is injected in entry points
    // based on the rendering backend used.
    //查看之前有没有虚拟dom
    if (!prevVnode) {
      // initial render
      vm.$el = vm.__patch__(vm.$el, vnode, hydrating, false /* removeOnly */)
    } else {
      // updates
      vm.$el = vm.__patch__(prevVnode, vnode)
    }
    restoreActiveInstance()
    // update __vue__ reference
    if (prevEl) {
      prevEl.__vue__ = null
    }
    if (vm.$el) {
      vm.$el.__vue__ = vm
    }
    // if parent is an HOC, update its $el as well
    if (vm.$vnode && vm.$parent && vm.$vnode === vm.$parent._vnode) {
      vm.$parent.$el = vm.$el
    }
    // updated hook is called by the scheduler to ensure that children are
    // updated in a parent's updated hook.
  }

挂载函数总结：

mountComponent()=>updateComponent()=>new Watcher()=>updateComponent()=>render()=>update()=>patch()

数据响应式

/Users/jerrychen/Desktop/vue-2.6/src/core/instance/state.js

 defineReactive

/Users/jerrychen/Desktop/vue-2.6/src/core/observer/index.js

export function defineReactive (
  obj: Object,
  key: string,
  val: any,
  customSetter?: ?Function,
  shallow?: boolean
) {
  //每个key对应一个dep
  const dep = new Dep()

  const property = Object.getOwnPropertyDescriptor(obj, key)
  if (property && property.configurable === false) {
    return
  }

  // cater for pre-defined getter/setters
  const getter = property && property.get
  const setter = property && property.set
  if ((!getter || setter) && arguments.length === 2) {
    val = obj[key]
  }

  let childOb = !shallow && observe(val)
  Object.defineProperty(obj, key, {
    enumerable: true,
    configurable: true,
    get: function reactiveGetter () {
      const value = getter ? getter.call(obj) : val
      if (Dep.target) {
        //依赖收集：vue2中一个组件对应一个watcher
        //dep和watcher是n=>1的关系
        //如果用户自己手动创建watcher，比如使用watch选项或者this.$watch(key,cb)
        // dep 1=>n
        dep.depend()
        if (childOb) {
          //子ob也要做依赖收集
          childOb.dep.depend()
          if (Array.isArray(value)) {
            dependArray(value)
          }
        }
      }
      return value
    },
    set: function reactiveSetter (newVal) {
      const value = getter ? getter.call(obj) : val
      /* eslint-disable no-self-compare */
      if (newVal === value || (newVal !== newVal && value !== value)) {
        return
      }
      /* eslint-enable no-self-compare */
      if (process.env.NODE_ENV !== 'production' && customSetter) {
        customSetter()
      }
      // #7981: for accessor properties without setter
      if (getter && !setter) return
      if (setter) {
        setter.call(obj, newVal)
      } else {
        val = newVal
      }
      childOb = !shallow && observe(newVal)
      dep.notify()
    }
  })
}

在收集依赖的过程中，使用depend方法

/Users/jerrychen/Desktop/vue-2.6/src/core/observer/dep.js

export default class Dep {
  static target: ?Watcher;
  id: number;
  subs: Array;

  constructor () {
    this.id = uid++
    this.subs = []
  }

  addSub (sub: Watcher) {
    this.subs.push(sub)
  }

  removeSub (sub: Watcher) {
    remove(this.subs, sub)
  }

  depend () {
    if (Dep.target) {
      //watcher的addDep
      Dep.target.addDep(this)
    }
  }

  notify () {
    // stabilize the subscriber list first
    const subs = this.subs.slice()
    if (process.env.NODE_ENV !== 'production' && !config.async) {
      // subs aren't sorted in scheduler if not running async
      // we need to sort them now to make sure they fire in correct
      // order
      subs.sort((a, b) => a.id - b.id)
    }
    for (let i = 0, l = subs.length; i < l; i++) {
      subs[i].update()
    }
  }
}

同时也会出现多个watcher对应多个dep的情况，所以互相添加引用

/Users/jerrychen/Desktop/vue-2.6/src/core/observer/watcher.js

  addDep (dep: Dep) {
    const id = dep.id
    //相互添加引用
    if (!this.newDepIds.has(id)) {
      //watcher添加dep
      this.newDepIds.add(id)
      this.newDeps.push(dep)
      if (!this.depIds.has(id)) {
        // dep添加watcher
        dep.addSub(this)
      }
    }
  }

以此来达到相互更新通知