[建议收藏] 你想知道的Vue3核心源码这里都有

Effect和Reactive

• Effect

  • 副作用依赖函数

• Track

  • 依赖收集

• Trigger

  • 依赖触发

Effect

• 先来看看入口函数

  • 入口函数主要是一些逻辑处理，核心逻辑位于createReactiveEffect

function effect<T = any>(
  fn: () => T,
  options: ReactiveEffectOptions = EMPTY_OBJ
): ReactiveEffect<T> {
  // 如果已经是effect，则重置
  if (isEffect(fn)) {
    fn = fn.raw
  }
  // 创建effect
  const effect = createReactiveEffect(fn, options)
  // 如果不是惰性执行，先执行一次
  if (!options.lazy) {
    effect()
  }
  return effect
}

• createReactiveEffect

const effectStack: ReactiveEffect[] = []

function createReactiveEffect<T = any>(
  fn: () => T,
  options: ReactiveEffectOptions
): ReactiveEffect<T> {
  const effect = function reactiveEffect(): unknown {
    // 没有激活，说明调用了effect stop函数
    if (!effect.active) {
      // 无调度者则直接返回，否则执行fn
      return options.scheduler ? undefined : fn()
    }
    // 判断EffectStack中有没有effect，有则不处理
    if (!effectStack.includes(effect)) {
      // 清除effect
      cleanup(effect)
      try {
        /*
        * 开始重新收集依赖
        * 压入stack
        * 将effect设置为activeEffect
        * */
        enableTracking()
        effectStack.push(effect)
        activeEffect = effect
        return fn()
      } finally {
        /*
        * 完成后将effect弹出
        * 重置依赖
        * 重置activeEffect
        * */
        effectStack.pop()
        resetTracking()
        activeEffect = effectStack[effectStack.length - 1]
      }
    }
  } as ReactiveEffect
  effect.id = uid++ // 自增id，effect唯一标识
  effect.allowRecurse = !!options.allowRecurse
  effect._isEffect = true // 是否是effect
  effect.active = true  // 是否激活
  effect.raw = fn   // 挂载原始对象
  effect.deps = []  // 当前effect的dep数组
  effect.options = options  // 传入的options
  return effect
}

// 每次effect运行都会重新收集依赖，deps是effect的依赖数组，需要全部清空
function cleanup(effect: ReactiveEffect) {
  const { deps } = effect
  if (deps.length) {
    for (let i = 0; i < deps.length; i++) {
      deps[i].delete(effect)
    }
    deps.length = 0
  }
}

Track

function track(target: object, type: TrackOpTypes, key: unknown) {
  // activeEffect为空表示没有依赖
  if (!shouldTrack || activeEffect === undefined) {
    return
  }

  // targetMap依赖管理Map，用于收集依赖
  // 检查targetMap中有没有target，没有则新建
  let depsMap = targetMap.get(target)
  if (!depsMap) {
    targetMap.set(target, (depsMap = new Map()))
  }

  // dep用来收集依赖函数，当监听的key值发生变化，触发dep中的依赖函数更新
  let dep = depsMap.get(key)
  if (!dep) {
    depsMap.set(key, (dep = new Set()))
  }
  if (!dep.has(activeEffect)) {
    dep.add(activeEffect)
    activeEffect.deps.push(dep)
    // 开发环境会触发onTrack，仅用于调试
    if (__DEV__ && activeEffect.options.onTrack) {
      activeEffect.options.onTrack({
        effect: activeEffect,
        target,
        type,
        key
      })
    }
  }
}

Trigger

function trigger(
  target: object,
  type: TriggerOpTypes,
  key?: unknown,
  newValue?: unknown,
  oldValue?: unknown,
  oldTarget?: Map<unknown, unknown> | Set<unknown>
) {
  // 获取依赖Map，如果没有则不需要触发
  const depsMap = targetMap.get(target)
  if (!depsMap) {
    // never been tracked
    return
  }

  // 使用Set保存需要触发的effect，避免重复
  const effects = new Set<ReactiveEffect>()
  // 定义依赖添加函数
  const add = (effectsToAdd: Set<ReactiveEffect> | undefined) => {
    if (effectsToAdd) {
      effectsToAdd.forEach(effect => {
        if (effect !== activeEffect || effect.allowRecurse) {
          effects.add(effect)
        }
      })
    }
  }

  // 将depsMap中的依赖添加到effects中
  // 只为了理解和原理的话   各个分支不用细看
  if (type === TriggerOpTypes.CLEAR) {
    // collection being cleared
    // trigger all effects for target
    depsMap.forEach(add)
  } else if (key === 'length' && isArray(target)) {
    depsMap.forEach((dep, key) => {
      if (key === 'length' || key >= (newValue as number)) {
        add(dep)
      }
    })
  } else {
    // schedule runs for SET | ADD | DELETE
    if (key !== void 0) {
      add(depsMap.get(key))
    }

    // also run for iteration key on ADD | DELETE | Map.SET
    switch (type) {
      case TriggerOpTypes.ADD:
        if (!isArray(target)) {
          add(depsMap.get(ITERATE_KEY))
          if (isMap(target)) {
            add(depsMap.get(MAP_KEY_ITERATE_KEY))
          }
        } else if (isIntegerKey(key)) {
          // new index added to array -> length changes
          add(depsMap.get('length'))
        }
        break
      case TriggerOpTypes.DELETE:
        if (!isArray(target)) {
          add(depsMap.get(ITERATE_KEY))
          if (isMap(target)) {
            add(depsMap.get(MAP_KEY_ITERATE_KEY))
          }
        }
        break
      case TriggerOpTypes.SET:
        if (isMap(target)) {
          add(depsMap.get(ITERATE_KEY))
        }
        break
    }
  }

  // 封装effects执行函数
  const run = (effect: ReactiveEffect) => {
    if (__DEV__ && effect.options.onTrigger) {
      effect.options.onTrigger({
        effect,
        target,
        key,
        type,
        newValue,
        oldValue,
        oldTarget
      })
    }
    // 如果存在scheduler则调用
    if (effect.options.scheduler) {
      effect.options.scheduler(effect)
    } else {
      effect()
    }
  }

  // 触发effects中的所有依赖函数
  effects.forEach(run)
}

Reactive

• 总结来说

  • 在getter时进行依赖收集
  • 在setter时触发依赖更新

function reactive(target:object){
    return new Proxy(target,{
        get(target: Target, key: string | symbol, receiver: object){
            const res = Reflect.get(target, key, receiver)
            track(target, TrackOpTypes.GET, key)
            return res
        }
        set(target: object, key: string | symbol, value: unknown, receiver: object){
            let oldValue = (target as any)[key]
            const result = Reflect.set(target, key, value, receiver)
            // trigger(target, TriggerOpTypes.ADD, key, value)
            trigger(target, TriggerOpTypes.SET, key, value, oldValue)
            return result
        }
    })
}

Computed

• Vue2

  • 在Vue2中Computed的实现通过嵌套watcher，实现响应式数据的依赖收集，间接链式触发依赖更新。

• Vue3中出现了effect，重新实现了Computed属性

  • effect可以被理解为副作用函数，被当做依赖收集，在响应式数据更新后被触发。

• 读完这段computed函数会发现，这里只是做了简要的getter和setter的赋值处理

  • computed支持两种写法

    • 函数
    • getter、setter

function computed<T>(
  getterOrOptions: ComputedGetter<T> | WritableComputedOptions<T>
) {
  let getter: ComputedGetter<T>
  let setter: ComputedSetter<T>

  if (isFunction(getterOrOptions)) {
    getter = getterOrOptions
    setter = __DEV__
      ? () => {
          console.warn('Write operation failed: computed value is readonly')
        }
      : NOOP
  } else {
    getter = getterOrOptions.get
    setter = getterOrOptions.set
  }

  return new ComputedRefImpl(
    getter,
    setter,
    isFunction(getterOrOptions) || !getterOrOptions.set
  ) as any
}

• 核心逻辑都在ComputedRefImpl中，我们接着往下看

  • 通过dirty变量标记数据是否为旧数据
  • 在响应式数据更新后将dirty赋值为true
  • 在下一次get时，dirty为true时进行重新计算，并将dirty赋值为false

class ComputedRefImpl<T> {
  private _value!: T
  private _dirty = true

  public readonly effect: ReactiveEffect<T>

  public readonly __v_isRef = true;
  public readonly [ReactiveFlags.IS_READONLY]: boolean

  constructor(
    getter: ComputedGetter<T>,
    private readonly _setter: ComputedSetter<T>,
    isReadonly: boolean
  ) {
    this.effect = effect(getter, {
      lazy: true,
      // 响应式数据更新后将dirty赋值为true
      // 下次执行getter判断dirty为true即重新计算computed值
      scheduler: () => {
        if (!this._dirty) {
          this._dirty = true
          // 派发所有引用当前计算属性的副作用函数effect
          trigger(toRaw(this), TriggerOpTypes.SET, 'value')
        }
      }
    })

    this[ReactiveFlags.IS_READONLY] = isReadonly
  }

  get value() {
    // the computed ref may get wrapped by other proxies e.g. readonly() #3376
    const self = toRaw(this)
    // 当响应式数据更新后dirty为true
    // 重新计算数据后，将dirty赋值为false
    if (self._dirty) {
      self._value = this.effect()
      self._dirty = false
    }
    // 依赖收集
    track(self, TrackOpTypes.GET, 'value')

    // 返回计算后的值
    return self._value
  }

  set value(newValue: T) {
    this._setter(newValue)
  }
}

Watch

• Watch

watch(state, (state, prevState)=>{})

• WatchEffect

const stop = watchEffect((onInvalidate)=>{
    // ...
    onInvalidate(()=>{
        // ...
    })
})
// 手动停止监听
stop()

watch和watchEffect的不同点

• watch惰性执行，watchEffect每次代码加载都会执行
• watch可指定监听变量，watchEffect自动依赖收集
• watch可获取新旧值，watchEffect不行
• watchEffect有onInvalidate功能，watch没有
• watch只可监听ref、reactive等对象，watchEffect只可监听具体属性

Source Code

• 这里可以看到watch和watchEffet的核心逻辑都封装到了doWatch中

// watch
export function watch<T = any, Immediate extends Readonly<boolean> = false>(
  source: T | WatchSource<T>,
  cb: any,
  options?: WatchOptions<Immediate>
): WatchStopHandle {
  if (__DEV__ && !isFunction(cb)) {
    warn(
      `\`watch(fn, options?)\` signature has been moved to a separate API. ` +
        `Use \`watchEffect(fn, options?)\` instead. \`watch\` now only ` +
        `supports \`watch(source, cb, options?) signature.`
    )
  }
  return doWatch(source as any, cb, options)
}

export function watchEffect(
  effect: WatchEffect,
  options?: WatchOptionsBase
): WatchStopHandle {
  return doWatch(effect, null, options)
}

• doWatch

function doWatch(
  source: WatchSource | WatchSource[] | WatchEffect | object,
  cb: WatchCallback | null,
  { immediate, deep, flush, onTrack, onTrigger }: WatchOptions = EMPTY_OBJ,
  instance = currentInstance
): WatchStopHandle {

  let getter: () => any
  let forceTrigger = false
  let isMultiSource = false

  // 对不同的情况做getter赋值
  if (isRef(source)) {
    // ref通过.value获取
    getter = () => (source as Ref).value
    forceTrigger = !!(source as Ref)._shallow
  } else if (isReactive(source)) {
    // reactive直接获取
    getter = () => source
    deep = true
  } else if (isArray(source)) {
    // 如果是数组，做遍历处理
    isMultiSource = true
    forceTrigger = source.some(isReactive)
    getter = () =>
      source.map(s => {
        if (isRef(s)) {
          return s.value
        } else if (isReactive(s)) {
          return traverse(s)
        } else if (isFunction(s)) {
          return callWithErrorHandling(s, instance, ErrorCodes.WATCH_GETTER, [
            instance && (instance.proxy as any)
          ])
        } else {
          __DEV__ && warnInvalidSource(s)
        }
      })
  } else if (isFunction(source)) {
    // 如果是函数的情况
    // 有cb则为watch，没有则为watchEffect
    if (cb) {
      // getter with cb
      getter = () =>
        callWithErrorHandling(source, instance, ErrorCodes.WATCH_GETTER, [
          instance && (instance.proxy as any)
        ])
    } else {
      // no cb -> simple effect
      getter = () => {
        if (instance && instance.isUnmounted) {
          return
        }
        if (cleanup) {
          cleanup()
        }
        return callWithAsyncErrorHandling(
          source,
          instance,
          ErrorCodes.WATCH_CALLBACK,
          [onInvalidate]
        )
      }
    }
  } else {
    // 异常情况
    getter = NOOP
    // 抛出异常
    __DEV__ && warnInvalidSource(source)
  }

  // 深度监听逻辑处理
  if (cb && deep) {
    const baseGetter = getter
    getter = () => traverse(baseGetter())
  }

  let cleanup: () => void
  let onInvalidate: InvalidateCbRegistrator = (fn: () => void) => {
    cleanup = runner.options.onStop = () => {
      callWithErrorHandling(fn, instance, ErrorCodes.WATCH_CLEANUP)
    }
  }

  // 记录oldValue，并通过runner获取newValue
  // callback的封装处理为job
  let oldValue = isMultiSource ? [] : INITIAL_WATCHER_VALUE
  const job: SchedulerJob = () => {
    if (!runner.active) {
      return
    }
    if (cb) {
      // watch(source, cb)
      const newValue = runner()
      if (
        deep ||
        forceTrigger ||
        (isMultiSource
          ? (newValue as any[]).some((v, i) =>
              hasChanged(v, (oldValue as any[])[i])
            )
          : hasChanged(newValue, oldValue)) ||
        (__COMPAT__ &&
          isArray(newValue) &&
          isCompatEnabled(DeprecationTypes.WATCH_ARRAY, instance))
      ) {
        // cleanup before running cb again
        if (cleanup) {
          cleanup()
        }
        callWithAsyncErrorHandling(cb, instance, ErrorCodes.WATCH_CALLBACK, [
          newValue,
          // pass undefined as the old value when it's changed for the first time
          oldValue === INITIAL_WATCHER_VALUE ? undefined : oldValue,
          onInvalidate
        ])
        oldValue = newValue
      }
    } else {
      // watchEffect
      runner()
    }
  }

  // important: mark the job as a watcher callback so that scheduler knows
  // it is allowed to self-trigger (#1727)
  job.allowRecurse = !!cb


  // 通过读取配置，处理job的触发时机
  // 并再次将job的执行封装到scheduler中
  let scheduler: ReactiveEffectOptions['scheduler']
  if (flush === 'sync') { // 同步执行
    scheduler = job
  } else if (flush === 'post') { // 更新后执行
    scheduler = () => queuePostRenderEffect(job, instance && instance.suspense)
  } else {
    // default: 'pre'
    // 更新前执行
    scheduler = () => {
      if (!instance || instance.isMounted) {
        queuePreFlushCb(job)
      } else {
        // with 'pre' option, the first call must happen before
        // the component is mounted so it is called synchronously.
        job()
      }
    }
  }

  // 使用effect副作用处理依赖收集，在依赖更新后调用scheduler（其中封装了callback的执行）
  const runner = effect(getter, {
    lazy: true,
    onTrack,
    onTrigger,
    scheduler
  })

  // 收集依赖
  recordInstanceBoundEffect(runner, instance)

  // 读取配置，进行watch初始化
  // 是否有cb
  if (cb) {
    // 是否立刻执行
    if (immediate) {
      job()
    } else {
      oldValue = runner()
    }
  } else if (flush === 'post') {
    // 是否更新后执行
    queuePostRenderEffect(runner, instance && instance.suspense)
  } else {
    runner()
  }

  // 返回手动停止函数
  return () => {
    stop(runner)
    if (instance) {
      remove(instance.effects!, runner)
    }
  }
}

Mixin

• 合并分为对象的合并和生命周期的合并

  • 对象，mergeOption

    • 类型Object.assign的合并，会出现覆盖现象

  • 生命周期，mergeHook

    • 合并会将两个生命周期放入一个队列，依次调用
• mergeOptions

function mergeOptions(
  to: any,
  from: any,
  instance?: ComponentInternalInstance | null,
  strats = instance && instance.appContext.config.optionMergeStrategies
) {
  if (__COMPAT__ && isFunction(from)) {
    from = from.options
  }

  const { mixins, extends: extendsOptions } = from

  extendsOptions && mergeOptions(to, extendsOptions, instance, strats)
  mixins &&
    mixins.forEach((m: ComponentOptionsMixin) =>
      mergeOptions(to, m, instance, strats)
    )

   // 对mixin中的对象进行遍历
  for (const key in from) {
    // 如果存在则进行覆盖处理
    if (strats && hasOwn(strats, key)) {
      to[key] = strats[key](to[key], from[key], instance && instance.proxy, key)
    } else {
    // 如果不存在则直接赋值
      to[key] = from[key]
    }
  }
  return to
}

• mergeHook

function mergeHook(
  to: Function[] | Function | undefined,
  from: Function | Function[]
) {
  return Array.from(new Set([...toArray(to), ...toArray(from)]))
}

Vuex4

快速过Vuex3.x原理

• 为什么每个组件都可以通过

this.$store访问到store数据？

• 在beforeCreate时，通过mixin的方式注入了store

• 为什么Vuex中的数据都是响应式的

  • 创建store的时候调用的是new Vue,创建了一个Vue实例，相当于借用了Vue的响应式。

• mapXxxx是怎么获取到store中的数据和方法的

  • mapXxxx只是一个语法糖，底层实现也是从$store中获取然后返回到computed / methods中。

Vuex4原理探究

createStore

• 从createStore开始看起

  • 可以发现Vuex4中的state是通过reactive API去创建的响应式数据，Vuex3中是通过new Vue实例
  • dispatch、commit的实现基本是封装了一层执行，不用过于关心

export function createStore (options) {
    return new Store(options)
}
class Store{
    constructor (options = {}){
        // 省略若干代码...
        this._modules = new ModuleCollection(options)
        const state = this._modules.root.state
        resetStoreState(this, state)

        // bind commit and dispatch to self
        const store = this
        const { dispatch, commit } = this
        this.dispatch = function boundDispatch (type, payload) {
          return dispatch.call(store, type, payload)
        }
        this.commit = function boundCommit (type, payload, options) {
          return commit.call(store, type, payload, options)
        }
        // 省略若干代码...
    }
}
function resetStoreState (store, state, hot) {
    // 省略若干代码...
    store._state = reactive({
        data: state
    })
    // 省略若干代码...
}

install

• Vuex是以插件的形式在Vue中使用的，在createApp时调用install安装

export function createAppAPI<HostElement>(
  render: RootRenderFunction,
  hydrate?: RootHydrateFunction
): CreateAppFunction<HostElement> {
  return function createApp(rootComponent, rootProps = null) {

    // 省略部分代码....
    const app: App = (context.app = {
      _uid: uid++,
      _component: rootComponent as ConcreteComponent,
      _props: rootProps,
      _container: null,
      _context: context,

      version,

      // 省略部分代码....

      use(plugin: Plugin, ...options: any[]) {
        if (installedPlugins.has(plugin)) {
          __DEV__ && warn(`Plugin has already been applied to target app.`)
        } else if (plugin && isFunction(plugin.install)) {
          installedPlugins.add(plugin)
          plugin.install(app, ...options)
        } else if (isFunction(plugin)) {
          installedPlugins.add(plugin)
          plugin(app, ...options)
        } else if (__DEV__) {
          warn(
            `A plugin must either be a function or an object with an "install" ` +
              `function.`
          )
        }
        return app
      },
      // 省略部分代码 ....
   }
}

• Store 类的install

  • 实现通过inject获取
  • 实现this.$store获取

install (app, injectKey) {
  // 实现通过inject获取
  app.provide(injectKey || storeKey, this)
  // 实现this.$store获取
  app.config.globalProperties.$store = this
}

app.provide实现

provide(key, value) {
  // 已存在则警告
  if (__DEV__ && (key as string | symbol) in context.provides) {
    warn(
      `App already provides property with key "${String(key)}". ` +
        `It will be overwritten with the new value.`
    )
  }

  // 将store放入context的provide中
  context.provides[key as string] = value
  return app
}

// context相关   context为上下文对象
const context = createAppContext()
export function createAppContext(): AppContext {
  return {
    app: null as any,
    config: {
      isNativeTag: NO,
      performance: false,
      globalProperties: {},
      optionMergeStrategies: {},
      errorHandler: undefined,
      warnHandler: undefined,
      compilerOptions: {}
    },
    mixins: [],
    components: {},
    directives: {},
    provides: Object.create(null)
  }
}

Vue.useStore

• 在Vue3 Composition API中使用Vuex

import { useStore } from 'vuex'

export default{
    setup(){
        const store = useStore();
    }
}

• useStore的实现

function useStore (key = null) {
  return inject(key !== null ? key : storeKey)
}

Vue.inject

• 通过provide时存入的key取出store
• 有父级实例则取父级实例的provides，没有则取根实例的provides

function inject(
  key: InjectionKey<any> | string,
  defaultValue?: unknown,
  treatDefaultAsFactory = false
) {
  const instance = currentInstance || currentRenderingInstance
  if (instance) {
    // 有父级实例则取父级实例的provides，没有则取根实例的provides
    const provides =
      instance.parent == null
        ? instance.vnode.appContext && instance.vnode.appContext.provides
        : instance.parent.provides

    // 通过provide时存入的key取出store
    if (provides && (key as string | symbol) in provides) {
      return provides[key as string]
    // 省略一部分代码......
  }
}

Vue.provide

• Vue的provide API也比较简单，相当于直接通过key/value赋值
• 当前实例provides和父级实例provides相同时，通过原型链建立连接

function provide<T>(key: InjectionKey<T> | string | number, value: T) {
  if (!currentInstance) {
    if (__DEV__) {
      warn(`provide() can only be used inside setup().`)
    }
  } else {
    let provides = currentInstance.provides
    const parentProvides =
      currentInstance.parent && currentInstance.parent.provides
    if (parentProvides === provides) {
      provides = currentInstance.provides = Object.create(parentProvides)
    }
    // TS doesn't allow symbol as index type
    provides[key as string] = value
  }
}

注入

• 为什么每个组件实例都有Store对象了?

  • 在创建组件实例的时候注入了provides

function createComponentInstance(vnode, parent, suspense) {
    const type = vnode.type;
    const appContext = (parent ? parent.appContext : vnode.appContext) || emptyAppContext;
    const instance = {
        parent,
        appContext,
        // ...
        provides: parent ? parent.provides : Object.create(appContext.provides),
        // ...
    }
    // ...
    return instance;
}

Diff算法优化

• Vue3中的主要优化点为

  • 在updateChildren时双端比较 -> 最长递增子序列
  • 全量Diff -> 静态标记 + 非全量Diff
  • 静态提升

updateChildren

• Vue2

  • 头 - 头比较
  • 尾 - 尾比较
  • 头 - 尾比较
  • 尾 - 头比较

• Vue3

  • 头 - 头比较
  • 尾 - 尾比较
  • 基于最长递增子序列进行移动 / 删除 / 新增

举个🌰

• oldChild [a,b,c,d,e,f,g]
• newChild [a,b,f,c,d,e,h,g]

1. 首先进行头 - 头比较,比较到不一样的节点时跳出循环

   • 得到[a,b]

2. 然后进行尾 - 尾比较，比较到不一样的节点时跳出循环

   • 得到[g]

3. 剩余[f,c,d,e,h]

   • 通过newIndexToOldIndexMap生成数组[5, 2, 3, 4, -1]
   • 得出最长递增子序列[2, 3, 4]对应节点为[c, d, e]
   • 剩余的节点基于[c, d, e]进行移动 / 新增 / 删除

静态标记

• patchFlag

export const enum PatchFlags{
  TEXT = 1 ,  //动态文本节点
  CLASS = 1 << 1, //2   动态class
  STYLE = 1 << 2, //4   动态style
  PROPS = 1 << 3, //8                动态属性，但不包含类名和样式
  FULL_PROPS = 1 << 4, //16   具有动态key属性，当key改变时，需进行完整的diff比较
  HYDRATE_EVENTS = 1 << 5,//32  带有监听事件的节点
  STABLE_FRAGMENT = 1 << 6, //64  一个不会改变子节点顺序的fragment
  KEYED_FRAGMENT = 1 << 7,  //128 带有key属性的fragment或部分子节点有key
  UNKEYEN_FRAGMENT = 1 << 8,   //256  子节点没有key的fragment
  NEED_PATCH = 1 << 9,   //512   一个节点只会进行非props比较
  DYNAMIC_SLOTS = 1 << 10,//1024   动态slot
  HOISTED = -1,   //静态节点
  //指示在diff过程中要退出优化模式
  BAIL = -2
}

举个🌰

• 模板长这样

<div>
  <p>Hello World</p>
  <p>{{msg}}</p>
</div>

• 生成vdom源码

import { createVNode as _createVNode, toDisplayString as _toDisplayString, openBlock as _openBlock, createBlock as _createBlock } from "vue"

export function render(_ctx, _cache, $props, $setup, $data, $options) {
  return (_openBlock(), _createBlock("div", null, [
    _createVNode("p", null, "Hello World"),
    _createVNode("p", null, _toDisplayString(_ctx.msg), 1 /* TEXT */)
  ]))
}

// Check the console for the AST

总结

• 对vnode进行标记，将需要动态更新和不需要动态更新的节点进行分类
• 静态节点仅需创建一次，渲染直接复用，不参与diff算法流程。

静态提升

• Vue2中无论是元素是否参与更新，每次都会重新创建
• Vue3中对于不参与更新的元素，只会被创建一次，之后会在每次渲染时候被不停地复用
• 以后每次进行render的时候，就不会重复创建这些静态的内容，而是直接从一开始就创建好的常量中取就行了。

import { createVNode as _createVNode, toDisplayString as _toDisplayString, openBlock as _openBlock, createBlock as _createBlock } from "vue"

/*
* 静态提升前
*/
export function render(_ctx, _cache, $props, $setup, $data, $options) {
  return (_openBlock(), _createBlock("div", null, [
    _createVNode("p", null, "Xmo"),
    _createVNode("p", null, "Xmo"),
    _createVNode("p", null, "Xmo"),
    _createVNode("p", null, _toDisplayString(_ctx.msg), 1 /* TEXT */)
  ]))
}

/*
* 静态提升后
*/
const _hoisted_1 = /*#__PURE__*/_createVNode("p", null, "Xmo", -1 /* HOISTED */)
const _hoisted_2 = /*#__PURE__*/_createVNode("p", null, "Xmo", -1 /* HOISTED */)
const _hoisted_3 = /*#__PURE__*/_createVNode("p", null, "Xmo", -1 /* HOISTED */)

export function render(_ctx, _cache, $props, $setup, $data, $options) {
  return (_openBlock(), _createBlock("div", null, [
    _hoisted_1,
    _hoisted_2,
    _hoisted_3,
    _createVNode("p", null, _toDisplayString(_ctx.msg), 1 /* TEXT */)
  ]))
}

// Check the console for the AST

cacheHandlers 事件侦听器缓存

• 默认情况下onClick会被视为动态绑定，所以每次都会去追踪它的变化
• 但是因为是同一个函数，所以没有追踪变化，直接缓存起来复用即可。

// 模板
<div>
  <button @click="onClick">btn</button>
</div>


// 使用缓存前
// 这里我们还没有开启事件监听缓存，熟悉的静态标记 8 /* PROPS */ 出现了，
// 它将标签的 Props （属性） 标记动态属性。
// 如果我们存在属性不会改变，不希望这个属性被标记为动态，那么就需要 cacheHandler 的出场了。
import { createVNode as _createVNode, openBlock as _openBlock, createBlock as _createBlock } from "vue"

export function render(_ctx, _cache, $props, $setup, $data, $options) {
  return (_openBlock(), _createBlock("div", null, [
    _createVNode("button", { onClick: _ctx.onClick }, "btn", 8 /* PROPS */, ["onClick"])
  ]))
}

// Check the console for the AST


// 使用缓存后
import { createVNode as _createVNode, openBlock as _openBlock, createBlock as _createBlock } from "vue"

export function render(_ctx, _cache, $props, $setup, $data, $options) {
  return (_openBlock(), _createBlock("div", null, [
    _createVNode("button", {
      onClick: _cache[1] || (_cache[1] = (...args) => (_ctx.onClick(...args)))
    }, "btn")
  ]))
}

// Check the console for the AST

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