How to use createApp in vue3
Function definition
The createApp function is defined in the file packages/runtime-dom/src/index.ts
export const createApp = ((...args) => { const app = ensureRenderer().createApp(...args) if (__DEV__) { injectNativeTagCheck(app) injectCompilerOptionsCheck(app) } const { mount } = app app.mount = (containerOrSelector: Element | ShadowRoot | string): any => { const container = normalizeContainer(containerOrSelector) if (!container) return const component = app._component if (!isFunction(component) && !component.render && !component.template) { // __UNSAFE__ // Reason: potential execution of JS expressions in in-DOM template. // The user must make sure the in-DOM template is trusted. If it's // rendered by the server, the template should not contain any user data. component.template = container.innerHTML // 2.x compat check if (__COMPAT__ && __DEV__) { for (let i = 0; i < container.attributes.length; i++) { const attr = container.attributes[i] if (attr.name !== 'v-cloak' && /^(v-|:|@)/.test(attr.name)) { compatUtils.warnDeprecation( DeprecationTypes.GLOBAL_MOUNT_CONTAINER, null ) break } } } } // clear content before mounting container.innerHTML = '' const proxy = mount(container, false, container instanceof SVGElement) if (container instanceof Element) { container.removeAttribute('v-cloak') container.setAttribute('data-v-app', '') } return proxy } return app }) as CreateAppFunction<Element>
(1) First create the App object
(2 ) Take out the mount method in the app object and rewrite the mount method
First call the normalizeContainer function to get the container node
Clear the innerHTML of the container
Call the original mount method
ensureRenderer
The function is defined as
function ensureRenderer() { return ( renderer || (renderer = createRenderer<Node, Element | ShadowRoot>(rendererOptions)) ) }
ensureRenderer calls createRenderer, and the createRenderer function is defined in the packages/runtime-core/src/renderer.ts file
export function createRenderer< HostNode = RendererNode, HostElement = RendererElement >(options: RendererOptions<HostNode, HostElement>) { return baseCreateRenderer<HostNode, HostElement>(options) }
Ultimately, baseCreateRenderer is called, which ultimately returns
return { render, hydrate, createApp: createAppAPI(render, hydrate) }
createAppAPI
The createAppAPI function is defined in the packages/runtime-core/src/apiCreateApp.ts file, and its return function
return function createApp(rootComponent, rootProps = null)
mount
is defined in packages/runtime- core/src/apiCreateApp.ts file
mount( rootContainer: HostElement, isHydrate?: boolean, isSVG?: boolean ): any { if (!isMounted) { const vnode = createVNode( rootComponent as ConcreteComponent, rootProps ) // store app context on the root VNode. // this will be set on the root instance on initial mount. vnode.appContext = context // HMR root reload if (__DEV__) { context.reload = () => { render(cloneVNode(vnode), rootContainer, isSVG) } } if (isHydrate && hydrate) { hydrate(vnode as VNode<Node, Element>, rootContainer as any) } else { render(vnode, rootContainer, isSVG) } isMounted = true app._container = rootContainer // for devtools and telemetry ;(rootContainer as any).__vue_app__ = app if (__DEV__ || __FEATURE_PROD_DEVTOOLS__) { app._instance = vnode.component devtoolsInitApp(app, version) } return vnode.component!.proxy } else if (__DEV__) { warn( `App has already been mounted.\n` + `If you want to remount the same app, move your app creation logic ` + `into a factory function and create fresh app instances for each ` + `mount - e.g. \`const createMyApp = () => createApp(App)\`` ) } }
(1) Call createVNode to create a virtual node
(2) Call the render function to implement rendering vnode. The render function is one of the parameters passed in when calling createAppAPI returned by the baseCreateRenderer function
// implementation function baseCreateRenderer( options: RendererOptions, createHydrationFns?: typeof createHydrationFunctions ): any { .... const render: RootRenderFunction = (vnode, container, isSVG) => { if (vnode == null) { if (container._vnode) { unmount(container._vnode, null, null, true) } } else { patch(container._vnode || null, vnode, container, null, null, null, isSVG) } flushPostFlushCbs() container._vnode = vnode } ..... }
patch
The function is defined in the packages/runtime-core/src/renderer.ts file
const patch: PatchFn = ( n1, n2, container, anchor = null, parentComponent = null, parentSuspense = null, isSVG = false, slotScopeIds = null, optimized = __DEV__ && isHmrUpdating ? false : !!n2.dynamicChildren ) => { // 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, slotScopeIds, optimized ) break default: if (shapeFlag & ShapeFlags.ELEMENT) { processElement( n1, n2, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } else if (shapeFlag & ShapeFlags.COMPONENT) { processComponent( n1, n2, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } else if (shapeFlag & ShapeFlags.TELEPORT) { ;(type as typeof TeleportImpl).process( n1 as TeleportVNode, n2 as TeleportVNode, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized, internals ) } else if (__FEATURE_SUSPENSE__ && shapeFlag & ShapeFlags.SUSPENSE) { ;(type as typeof SuspenseImpl).process( n1, n2, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized, internals ) } else if (__DEV__) { warn('Invalid VNode type:', type, `(${typeof type})`) } } // set ref if (ref != null && parentComponent) { setRef(ref, n1 && n1.ref, parentSuspense, n2 || n1, !n2) } } const patch: PatchFn = ( n1, n2, container, anchor = null, parentComponent = null, parentSuspense = null, isSVG = false, slotScopeIds = null, optimized = __DEV__ && isHmrUpdating ? false : !!n2.dynamicChildren ) => { // patching & not same type, unmount old tree if (n1 && !isSameVNodeType(n1, n2)) { anchor = getNextHostNode(n1) unmount(n1, parentComponent, parentSuspense, true) n1 = null } if (n2.patchFlag === PatchFlags.BAIL) { optimized = false n2.dynamicChildren = null } const { type, ref, shapeFlag } = n2 switch (type) { case Text: processText(n1, n2, container, anchor) break case Comment: processCommentNode(n1, n2, container, anchor) break case Static: if (n1 == null) { mountStaticNode(n2, container, anchor, isSVG) } else if (__DEV__) { patchStaticNode(n1, n2, container, isSVG) } break case Fragment: processFragment( n1, n2, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) break default: if (shapeFlag & ShapeFlags.ELEMENT) { processElement( n1, n2, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } else if (shapeFlag & ShapeFlags.COMPONENT) { processComponent( n1, n2, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } else if (shapeFlag & ShapeFlags.TELEPORT) { ;(type as typeof TeleportImpl).process( n1 as TeleportVNode, n2 as TeleportVNode, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized, internals ) } else if (__FEATURE_SUSPENSE__ && shapeFlag & ShapeFlags.SUSPENSE) { ;(type as typeof SuspenseImpl).process( n1, n2, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized, internals ) } else if (__DEV__) { warn('Invalid VNode type:', type, `(${typeof type})`) } } // set ref if (ref != null && parentComponent) { setRef(ref, n1 && n1.ref, parentSuspense, n2 || n1, !n2) } }
processComponent
The function is defined in the packages/runtime-core/src/renderer.ts file
const processComponent = ( n1: VNode | null, n2: VNode, container: RendererElement, anchor: RendererNode | null, parentComponent: ComponentInternalInstance | null, parentSuspense: SuspenseBoundary | null, isSVG: boolean, slotScopeIds: string[] | null, optimized: boolean ) => { n2.slotScopeIds = slotScopeIds if (n1 == null) { if (n2.shapeFlag & ShapeFlags.COMPONENT_KEPT_ALIVE) { ;(parentComponent!.ctx as KeepAliveContext).activate( n2, container, anchor, isSVG, optimized ) } else { mountComponent( n2, container, anchor, parentComponent, parentSuspense, isSVG, optimized ) } } else { updateComponent(n1, n2, optimized) } }
Compare the old and new virtual nodes n1 and n2. If n1 is empty, mount the node ; Otherwise, update the node. At this time n1 is empty, execute mountComponent to mount the node
mountComponent
The function is defined in the packages/runtime-core/src/renderer.ts file
const mountComponent: MountComponentFn = ( initialVNode, container, anchor, parentComponent, parentSuspense, isSVG, optimized ) => { // 2.x compat may pre-creaate the component instance before actually // mounting const compatMountInstance = __COMPAT__ && initialVNode.isCompatRoot && initialVNode.component const instance: ComponentInternalInstance = compatMountInstance || (initialVNode.component = createComponentInstance( initialVNode, parentComponent, parentSuspense )) // inject renderer internals for keepAlive if (isKeepAlive(initialVNode)) { ;(instance.ctx as KeepAliveContext).renderer = internals } // resolve props and slots for setup context if (!(__COMPAT__ && compatMountInstance)) { setupComponent(instance) } // 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 } setupRenderEffect( instance, initialVNode, container, anchor, parentSuspense, isSVG, optimized ) }
its execution The process is
(1) First call createComponentInstance to create an instance object of the component
(2) Call setupComponent to initialize properties and slots properties
(3) Call setup and rendering The side effect function setupRenderEffect mainly executes the run method of ReactiveEffect to execute componentUpdateFn and schedule queueJob.
setupRenderEffect
The function is defined in the packages/runtime-core/src/renderer.ts file. The key is the function componentUpdateFn
const componentUpdateFn = () => { if (!instance.isMounted) { let vnodeHook: VNodeHook | null | undefined const { el, props } = initialVNode const { bm, m, parent } = instance effect.allowRecurse = false // beforeMount hook if (bm) { invokeArrayFns(bm) } // onVnodeBeforeMount if ((vnodeHook = props && props.onVnodeBeforeMount)) { invokeVNodeHook(vnodeHook, parent, initialVNode) } if ( __COMPAT__ && isCompatEnabled(DeprecationTypes.INSTANCE_EVENT_HOOKS, instance) ) { instance.emit('hook:beforeMount') } effect.allowRecurse = true if (el && hydrateNode) { // vnode has adopted host node - perform hydration instead of mount. const hydrateSubTree = () => { instance.subTree = renderComponentRoot(instance) hydrateNode!( el as Node, instance.subTree, instance, parentSuspense, null ) } if (isAsyncWrapper(initialVNode)) { (initialVNode.type as ComponentOptions).__asyncLoader!().then( // note: we are moving the render call into an async callback, // which means it won't track dependencies - but it's ok because // a server-rendered async wrapper is already in resolved state // and it will never need to change. () => !instance.isUnmounted && hydrateSubTree() ) } else { hydrateSubTree() } } else { const subTree = (instance.subTree = renderComponentRoot(instance)) patch( null, subTree, container, anchor, instance, parentSuspense, isSVG ) initialVNode.el = subTree.el } // mounted hook if (m) { queuePostRenderEffect(m, parentSuspense) } // onVnodeMounted if ((vnodeHook = props && props.onVnodeMounted)) { const scopedInitialVNode = initialVNode queuePostRenderEffect( () => invokeVNodeHook(vnodeHook!, parent, scopedInitialVNode), parentSuspense ) } if ( __COMPAT__ && isCompatEnabled(DeprecationTypes.INSTANCE_EVENT_HOOKS, instance) ) { queuePostRenderEffect( () => instance.emit('hook:mounted'), parentSuspense ) } // activated hook for keep-alive roots. // #1742 activated hook must be accessed after first render // since the hook may be injected by a child keep-alive if (initialVNode.shapeFlag & ShapeFlags.COMPONENT_SHOULD_KEEP_ALIVE) { instance.a && queuePostRenderEffect(instance.a, parentSuspense) if ( __COMPAT__ && isCompatEnabled(DeprecationTypes.INSTANCE_EVENT_HOOKS, instance) ) { queuePostRenderEffect( () => instance.emit('hook:activated'), parentSuspense ) } } instance.isMounted = true // #2458: deference mount-only object parameters to prevent memleaks initialVNode = container = anchor = null as any } else { // updateComponent // This is triggered by mutation of component's own state (next: null) // OR parent calling processComponent (next: VNode) let { next, bu, u, parent, vnode } = instance let originNext = next let vnodeHook: VNodeHook | null | undefined if (next) { next.el = vnode.el updateComponentPreRender(instance, next, optimized) } else { next = vnode } // Disallow component effect recursion during pre-lifecycle hooks. effect.allowRecurse = false // beforeUpdate hook if (bu) { invokeArrayFns(bu) } // onVnodeBeforeUpdate if ((vnodeHook = next.props && next.props.onVnodeBeforeUpdate)) { invokeVNodeHook(vnodeHook, parent, next, vnode) } if ( __COMPAT__ && isCompatEnabled(DeprecationTypes.INSTANCE_EVENT_HOOKS, instance) ) { instance.emit('hook:beforeUpdate') } effect.allowRecurse = true // render const nextTree = renderComponentRoot(instance) const prevTree = instance.subTree instance.subTree = nextTree patch( prevTree, nextTree, // parent may have changed if it's in a teleport hostParentNode(prevTree.el!)!, // anchor may have changed if it's in a fragment getNextHostNode(prevTree), instance, parentSuspense, isSVG ) next.el = nextTree.el if (originNext === null) { // self-triggered update. In case of HOC, update parent component // vnode el. HOC is indicated by parent instance's subTree pointing // to child component's vnode updateHOCHostEl(instance, nextTree.el) } // updated hook if (u) { queuePostRenderEffect(u, parentSuspense) } // onVnodeUpdated if ((vnodeHook = next.props && next.props.onVnodeUpdated)) { queuePostRenderEffect( () => invokeVNodeHook(vnodeHook!, parent, next!, vnode), parentSuspense ) } if ( __COMPAT__ && isCompatEnabled(DeprecationTypes.INSTANCE_EVENT_HOOKS, instance) ) { queuePostRenderEffect( () => instance.emit('hook:updated'), parentSuspense ) } } }
When the component has not been When mounting, you need to mount it, and after the mounting is completed, set the component's isMounted attribute to true to indicate that the component has been successfully mounted. If already mounted, update the component.
Recursively call the patch function to mount the component
processFragment
The function is defined in the packages/runtime-core/src/renderer.ts file
const processFragment = ( n1: VNode | null, n2: VNode, container: RendererElement, anchor: RendererNode | null, parentComponent: ComponentInternalInstance | null, parentSuspense: SuspenseBoundary | null, isSVG: boolean, slotScopeIds: string[] | null, optimized: boolean ) => { const fragmentStartAnchor = (n2.el = n1 ? n1.el : hostCreateText(''))! const fragmentEndAnchor = (n2.anchor = n1 ? n1.anchor : hostCreateText(''))! let { patchFlag, dynamicChildren, slotScopeIds: fragmentSlotScopeIds } = n2 if (dynamicChildren) { optimized = true } // check if this is a slot fragment with :slotted scope ids if (fragmentSlotScopeIds) { slotScopeIds = slotScopeIds ? slotScopeIds.concat(fragmentSlotScopeIds) : fragmentSlotScopeIds } if (n1 == null) { hostInsert(fragmentStartAnchor, container, anchor) hostInsert(fragmentEndAnchor, container, anchor) // a fragment can only have array children // since they are either generated by the compiler, or implicitly created // from arrays. mountChildren( n2.children as VNodeArrayChildren, container, fragmentEndAnchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } else { if ( patchFlag > 0 && patchFlag & PatchFlags.STABLE_FRAGMENT && dynamicChildren && // #2715 the previous fragment could've been a BAILed one as a result // of renderSlot() with no valid children n1.dynamicChildren ) { // a stable fragment (template root or <template v-for>) doesn't need to // patch children order, but it may contain dynamicChildren. patchBlockChildren( n1.dynamicChildren, dynamicChildren, container, parentComponent, parentSuspense, isSVG, slotScopeIds ) if (__DEV__ && parentComponent && parentComponent.type.__hmrId) { traverseStaticChildren(n1, n2) } else if ( // #2080 if the stable fragment has a key, it's a <template v-for> that may // get moved around. Make sure all root level vnodes inherit el. // #2134 or if it's a component root, it may also get moved around // as the component is being moved. n2.key != null || (parentComponent && n2 === parentComponent.subTree) ) { traverseStaticChildren(n1, n2, true /* shallow */) } } else { // keyed / unkeyed, or manual fragments. // for keyed & unkeyed, since they are compiler generated from v-for, // each child is guaranteed to be a block so the fragment will never // have dynamicChildren. patchChildren( n1, n2, container, fragmentEndAnchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } } }
( 1) If n1 is empty, execute mountChildren
(2) Otherwise execute patchChildren
mountChildren
function defined in packages/runtime-core/src/renderer.ts file Middle
const mountChildren: MountChildrenFn = ( children, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized, start = 0 ) => { for (let i = start; i < children.length; i++) { const child = (children[i] = optimized ? cloneIfMounted(children[i] as VNode) : normalizeVNode(children[i])) patch( null, child, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } }
Traverse children and execute patch to mount all child elements
processElement
The function is defined in the packages/runtime-core/src/renderer.ts file
const processElement = ( n1: VNode | null, n2: VNode, container: RendererElement, anchor: RendererNode | null, parentComponent: ComponentInternalInstance | null, parentSuspense: SuspenseBoundary | null, isSVG: boolean, slotScopeIds: string[] | null, optimized: boolean ) => { isSVG = isSVG || (n2.type as string) === 'svg' if (n1 == null) { mountElement( n2, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } else { patchElement( n1, n2, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } }
(1) If n1 is empty, call mountElement to mount the element
(2) If n1 is not empty, call patchElement to update the element
At this time, execute the mount load element.
mountElement
The function is defined in the packages/runtime-core/src/renderer.ts file
const processElement = ( n1: VNode | null, n2: VNode, container: RendererElement, anchor: RendererNode | null, parentComponent: ComponentInternalInstance | null, parentSuspense: SuspenseBoundary | null, isSVG: boolean, slotScopeIds: string[] | null, optimized: boolean ) => { isSVG = isSVG || (n2.type as string) === 'svg' if (n1 == null) { mountElement( n2, container, anchor, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } else { patchElement( n1, n2, parentComponent, parentSuspense, isSVG, slotScopeIds, optimized ) } }
(1) Call hostCreateElement to create a DOM element based on the type and other attributes Node
(2) Determine the type of the child node. If the child node is plain text, the plain text hostSetElementText is processed directly. If the child node is an array, the mountChildren function is called to deeply traverse the child node
( 3) Process props attributes, mainly calling hostPatchProp and setScopeId
(4) Call hostInsert to mount el into the container
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