// wrapper function for providing a more flexible interface // without getting yelled at by flow exportfunctioncreateElement ( context: Component, tag: any, data: any, children: any, normalizationType: any, alwaysNormalize: boolean ): VNode | Array<VNode> { if (Array.isArray(data) || isPrimitive(data)) { normalizationType = children children = data data = undefined } if (isTrue(alwaysNormalize)) { normalizationType = ALWAYS_NORMALIZE } return _createElement(context, tag, data, children, normalizationType) }
exportfunction_createElement ( context: Component, tag?: string | Class<Component> | Function | Object, data?: VNodeData, children?: any, normalizationType?: number ): VNode | Array<VNode> { if (isDef(data) && isDef((data: any).__ob__)) { process.env.NODE_ENV !== 'production' && warn( `Avoid using observed data object as vnode data: ${JSON.stringify(data)}\n`` + 'Always create fresh vnode data objects in each render!', context ) return createEmptyVNode() } // object syntax in v-bind if (isDef(data) && isDef(data.is)) { tag = data.is } if (!tag) { // in case of component :is set to falsy value return createEmptyVNode() } // warn against non-primitive key if (process.env.NODE_ENV !== 'production' && isDef(data) && isDef(data.key) && !isPrimitive(data.key) ) { if (!__WEEX__ || !('@binding' in data.key)) { warn( 'Avoid using non-primitive value as key, ' + 'use string/number value instead.', context ) } } // support single function children as default scoped slot if (Array.isArray(children) && typeof children[0] === 'function' ) { data = data || {} data.scopedSlots = { default: children[0] } children.length = 0 } if (normalizationType === ALWAYS_NORMALIZE) { children = normalizeChildren(children) } else if (normalizationType === SIMPLE_NORMALIZE) { children = simpleNormalizeChildren(children) } let vnode, ns if (typeof tag === 'string') { let Ctor ns = (context.$vnode && context.$vnode.ns) || config.getTagNamespace(tag) if (config.isReservedTag(tag)) { // platform built-in elements vnode = new VNode( config.parsePlatformTagName(tag), data, children, undefined, undefined, context ) } else if (isDef(Ctor = resolveAsset(context.$options, 'components', tag))) { // component vnode = createComponent(Ctor, data, context, children, tag) } else { // unknown or unlisted namespaced elements // check at runtime because it may get assigned a namespace when its // parent normalizes children vnode = new VNode( tag, data, children, undefined, undefined, context ) } } else { // direct component options / constructor vnode = createComponent(tag, data, context, children) } if (Array.isArray(vnode)) { return vnode } else if (isDef(vnode)) { if (isDef(ns)) applyNS(vnode, ns) if (isDef(data)) registerDeepBindings(data) return vnode } else { return createEmptyVNode() } }
// The template compiler attempts to minimize the need for normalization by // statically analyzing the template at compile time. // // For plain HTML markup, normalization can be completely skipped because the // generated render function is guaranteed to return Array<VNode>. There are // two cases where extra normalization is needed:
// 1. When the children contains components - because a functional component // may return an Array instead of a single root. In this case, just a simple // normalization is needed - if any child is an Array, we flatten the whole // thing with Array.prototype.concat. It is guaranteed to be only 1-level deep // because functional components already normalize their own children. exportfunctionsimpleNormalizeChildren (children: any) { for (let i = 0; i < children.length; i++) { if (Array.isArray(children[i])) { returnArray.prototype.concat.apply([], children) } } return children }
// 2. When the children contains constructs that always generated nested Arrays, // e.g. <template>, <slot>, v-for, or when the children is provided by user // with hand-written render functions / JSX. In such cases a full normalization // is needed to cater to all possible types of children values. exportfunctionnormalizeChildren (children: any): ?Array<VNode> { return isPrimitive(children) ? [createTextVNode(children)] : Array.isArray(children) ? normalizeArrayChildren(children) : undefined }
functionnormalizeArrayChildren (children: any, nestedIndex?: string): Array<VNode> { const res = [] let i, c, lastIndex, last for (i = 0; i < children.length; i++) { c = children[i] if (isUndef(c) || typeof c === 'boolean') continue lastIndex = res.length - 1 last = res[lastIndex] // nested if (Array.isArray(c)) { if (c.length > 0) { c = normalizeArrayChildren(c, `${nestedIndex || ''}_${i}`) // merge adjacent text nodes if (isTextNode(c[0]) && isTextNode(last)) { res[lastIndex] = createTextVNode(last.text + (c[0]: any).text) c.shift() } res.push.apply(res, c) } } elseif (isPrimitive(c)) { if (isTextNode(last)) { // merge adjacent text nodes // this is necessary for SSR hydration because text nodes are // essentially merged when rendered to HTML strings res[lastIndex] = createTextVNode(last.text + c) } elseif (c !== '') { // convert primitive to vnode res.push(createTextVNode(c)) } } else { if (isTextNode(c) && isTextNode(last)) { // merge adjacent text nodes res[lastIndex] = createTextVNode(last.text + c.text) } else { // default key for nested array children (likely generated by v-for) if (isTrue(children._isVList) && isDef(c.tag) && isUndef(c.key) && isDef(nestedIndex)) { c.key = `__vlist${nestedIndex}_${i}__` } res.push(c) } } } return res }