return {
    render,
    hydrate,
    createApp: createAppAPI(render, hydrate)
  }

 const render: RootRenderFunction = (vnode, container) => {
    if (vnode == null) {
      if (container._vnode) {
        unmount(container._vnode, null, null, true)
      }
    } else {
      patch(container._vnode || null, vnode, container)
    }
    flushPostFlushCbs()
    container._vnode = vnode
  }

 const patch: PatchFn = (
    n1,
    n2,
    container,
    anchor = null,
    parentComponent = null,
    parentSuspense = null,
    isSVG = false,
    optimized = false
  ) => {
    // patching & not same type, unmount old tree
    if (n1 && !isSameVNodeType(n1, n2)) {
      anchor = getNextHostNode(n1)
      unmount(n1, parentComponent, parentSuspense, true)
      n1 = null
    }

    if (n2.patchFlag === PatchFlags.BAIL) {
      optimized = false
      n2.dynamicChildren = null
    }

    const { type, ref, shapeFlag } = n2
    switch (type) {
      case Text:
        processText(n1, n2, container, anchor)
        break
      case Comment:
        processCommentNode(n1, n2, container, anchor)
        break
      case Static:
        if (n1 == null) {
          mountStaticNode(n2, container, anchor, isSVG)
        } else if (__DEV__) {
          patchStaticNode(n1, n2, container, isSVG)
        }
        break
      case Fragment:
        processFragment(
          n1,
          n2,
          container,
          anchor,
          parentComponent,
          parentSuspense,
          isSVG,
          optimized
        )
        break
      default:
        if (shapeFlag & ShapeFlags.ELEMENT) {
          processElement(
            n1,
            n2,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            isSVG,
            optimized
          )
        } else if (shapeFlag & ShapeFlags.COMPONENT) {
          // 初始化走這個(gè)
          processComponent(
            n1,
            n2,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            isSVG,
            optimized
          )
        } else if (shapeFlag & ShapeFlags.TELEPORT) {
          ;(type as typeof TeleportImpl).process(
            n1 as TeleportVNode,
            n2 as TeleportVNode,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            isSVG,
            optimized,
            internals
          )
        } else if (__FEATURE_SUSPENSE__ && shapeFlag & ShapeFlags.SUSPENSE) {
          ;(type as typeof SuspenseImpl).process(
            n1,
            n2,
            container,
            anchor,
            parentComponent,
            parentSuspense,
            isSVG,
            optimized,
            internals
          )
        } else if (__DEV__) {
          warn('Invalid VNode type:', type, `(${typeof type})`)
        }
    }

    // set ref
    if (ref != null && parentComponent) {
      setRef(ref, n1 && n1.ref, parentComponent, parentSuspense, n2)
    }
  }

 const processComponent = (
    n1: VNode | null,
    n2: VNode,
    container: RendererElement,
    anchor: RendererNode | null,
    parentComponent: ComponentInternalInstance | null,
    parentSuspense: SuspenseBoundary | null,
    isSVG: boolean,
    optimized: boolean
  ) => {
    if (n1 == null) {
      if (n2.shapeFlag & ShapeFlags.COMPONENT_KEPT_ALIVE) {
        ;(parentComponent!.ctx as KeepAliveContext).activate(
          n2,
          container,
          anchor,
          isSVG,
          optimized
        )
      } else {
        // 初始化走掛載流程
        mountComponent(
          n2,
          container,
          anchor,
          parentComponent,
          parentSuspense,
          isSVG,
          optimized
        )
      }
    } else {
      updateComponent(n1, n2, optimized)
    }
  }

const mountComponent: MountComponentFn = (
    initialVNode,
    container,
    anchor,
    parentComponent,
    parentSuspense,
    isSVG,
    optimized
  ) => {
    // 創(chuàng)建組件實(shí)例
    const instance: ComponentInternalInstance = (initialVNode.component = createComponentInstance(
      initialVNode,
      parentComponent,
      parentSuspense
    ))

    if (__DEV__ && instance.type.__hmrId) {
      registerHMR(instance)
    }

    if (__DEV__) {
      pushWarningContext(initialVNode)
      startMeasure(instance, `mount`)
    }

    // inject renderer internals for keepAlive
    if (isKeepAlive(initialVNode)) {
      ;(instance.ctx as KeepAliveContext).renderer = internals
    }

    // resolve props and slots for setup context
    if (__DEV__) {
      startMeasure(instance, `init`)
    }
    // 安裝組件：選項(xiàng)處理
    setupComponent(instance)
    if (__DEV__) {
      endMeasure(instance, `init`)
    }

    // setup() is async. This component relies on async logic to be resolved
    // before proceeding
    if (__FEATURE_SUSPENSE__ && instance.asyncDep) {
      parentSuspense && parentSuspense.registerDep(instance, setupRenderEffect)

      // Give it a placeholder if this is not hydration
      // TODO handle self-defined fallback
      if (!initialVNode.el) {
        const placeholder = (instance.subTree = createVNode(Comment))
        processCommentNode(null, placeholder, container!, anchor)
      }
      return
    }

    // 建立渲染函數(shù)副作用：依賴收集
    setupRenderEffect(
      instance,
      initialVNode,
      container,
      anchor,
      parentSuspense,
      isSVG,
      optimized
    )

    if (__DEV__) {
      popWarningContext()
      endMeasure(instance, `mount`)
    }
  }

export function setupComponent(
  instance: ComponentInternalInstance,
  isSSR = false
) {
  isInSSRComponentSetup = isSSR

  const { props, children, shapeFlag } = instance.vnode
  const isStateful = shapeFlag & ShapeFlags.STATEFUL_COMPONENT
  initProps(instance, props, isStateful, isSSR)
  initSlots(instance, children)

  const setupResult = isStateful
    ? setupStatefulComponent(instance, isSSR)
    : undefined
  isInSSRComponentSetup = false
  return setupResult
}

function setupStatefulComponent(
  instance: ComponentInternalInstance,
  isSSR: boolean
) {
  // 組件配置
  const Component = instance.type as ComponentOptions

  if (__DEV__) {
    if (Component.name) {
      validateComponentName(Component.name, instance.appContext.config)
    }
    if (Component.components) {
      const names = Object.keys(Component.components)
      for (let i = 0; i < names.length; i++) {
        validateComponentName(names[i], instance.appContext.config)
      }
    }
    if (Component.directives) {
      const names = Object.keys(Component.directives)
      for (let i = 0; i < names.length; i++) {
        validateDirectiveName(names[i])
      }
    }
  }
  // 0. create render proxy property access cache
  instance.accessCache = {}
  // 1. create public instance / render proxy
  // also mark it raw so it's never observed
  instance.proxy = new Proxy(instance.ctx, PublicInstanceProxyHandlers)
  if (__DEV__) {
    exposePropsOnRenderContext(instance)
  }
  // 2. call setup()
  const { setup } = Component
  if (setup) {
    const setupContext = (instance.setupContext =
      setup.length > 1 ? createSetupContext(instance) : null)

    currentInstance = instance
    pauseTracking()
    const setupResult = callWithErrorHandling(
      setup,
      instance,
      ErrorCodes.SETUP_FUNCTION,
      [__DEV__ ? shallowReadonly(instance.props) : instance.props, setupContext]
    )
    resetTracking()
    currentInstance = null

    if (isPromise(setupResult)) {
      if (isSSR) {
        // return the promise so server-renderer can wait on it
        return setupResult.then((resolvedResult: unknown) => {
          handleSetupResult(instance, resolvedResult, isSSR)
        })
      } else if (__FEATURE_SUSPENSE__) {
        // async setup returned Promise.
        // bail here and wait for re-entry.
        instance.asyncDep = setupResult
      } else if (__DEV__) {
        warn(
          `setup() returned a Promise, but the version of Vue you are using ` +
            `does not support it yet.`
        )
      }
    } else {
      handleSetupResult(instance, setupResult, isSSR)
    }
  } else {
    // 處理選項(xiàng)等事務(wù)
    finishComponentSetup(instance, isSSR)
  }
}

  // support for 2.x options
  // 支持選項(xiàng)API
  if (__FEATURE_OPTIONS_API__) {
    currentInstance = instance
    applyOptions(instance, Component)
    currentInstance = null
  }

  // options initialization order (to be consistent with Vue 2):
  // - props (already done outside of this function)
  // - inject
  // - methods
  // - data (deferred since it relies on `this` access)
  // - computed
  // - watch (deferred since it relies on `this` access)

  if (!asMixin) {
    if (deferredData.length) {
      deferredData.forEach(dataFn => resolveData(instance, dataFn, publicThis))
    }
    if (dataOptions) {
      // 數(shù)據(jù)響應(yīng)式
      resolveData(instance, dataOptions, publicThis)
    }

function resolveData(
  instance: ComponentInternalInstance,
  dataFn: DataFn,
  publicThis: ComponentPublicInstance
) {
  if (__DEV__ && !isFunction(dataFn)) {
    warn(
      `The data option must be a function. ` +
        `Plain object usage is no longer supported.`
    )
  }
  // 獲取數(shù)據(jù)對象
  const data = dataFn.call(publicThis, publicThis)
  if (__DEV__ && isPromise(data)) {
    warn(
      `data() returned a Promise - note data() cannot be async; If you ` +
        `intend to perform data fetching before component renders, use ` +
        `async setup() + <Suspense>.`
    )
  }
  if (!isObject(data)) {
    __DEV__ && warn(`data() should return an object.`)
  } else if (instance.data === EMPTY_OBJ) {
    // 對data 做響應(yīng)式處理
    instance.data = reactive(data)
  } else {
    // existing data: this is a mixin or extends.
    extend(instance.data, data)
  }
}

  return createReactiveObject(
    target,
    false,
    mutableHandlers,
    mutableCollectionHandlers
  )

  instance.update = effect(function componentEffect() {
      if (!instance.isMounted) {
        let vnodeHook: VNodeHook | null | undefined
        const { el, props } = initialVNode
        const { bm, m, parent } = instance

        const subTree = (instance.subTree = renderComponentRoot(instance))