export function unmount (vnode, parentDom?) {
  if (isInvalid(vnode)) {
    return
  }
  const vtype = vnode.vtype
  // Bitwise operators for better performance
  // see: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators
  const dom = vtype & VType.Composite ? vnode.component.dom : vnode.dom

  if ((vtype & (VType.Composite | VType.Stateless)) > 0) {
    options.beforeUnmount(vnode)
    vnode.destroy()
  } else if ((vtype & VType.Node) > 0) {
    const { props, children, ref } = vnode
    unmountChildren(children)
    for (const propName in props) {
      if (isAttrAnEvent(propName)) {
        detachEvent(dom, propName, props[propName])
      }
    }
    if (ref !== null) {
      Ref.detach(vnode, ref, dom)
    }
  }

  if (!isNullOrUndef(parentDom) && !isNullOrUndef(dom)) {
    parentDom.removeChild(dom)
  }
  // vnode.dom = null
}

 vnode.forEach((child) => {
   if (!isInvalid(child)) {
     const childNode = createElement(child, isSvg, parentContext, parentComponent)
     if (childNode) {
       domNode.appendChild(childNode)
     }
   }
 })

function isSameVNode (a, b) {
  if (isInvalid(a) || isInvalid(b)) {
    return false
  }
  return a.type === b.type && a.key === b.key
}

    return children.map(fn)
  },
  forEach (
    children: Array<VirtualChildren | any>,
    fn: IterateFn,
    ctx: any
  ): void {
    if (isNullOrUndef(children)) {
      return
    }
    children = Children.toArray(children)
    if (ctx && ctx !== children) {
      fn = fn.bind(ctx)
    }
    for (let i = 0, len = children.length; i < len; i++) {
      const child = isInvalid(children[i]) ? null : children[i]

      fn(child, i, children)
    }
  },
  count (children: Array<VirtualChildren | any>): number {
    children = Children.toArray(children)
    return children.length
  },
  only (children: Array<VirtualChildren | any>): VirtualChildren | any {
    children = Children.toArray(children)
    if (children.length !== 1) {
      throw new Error('Children.only() expects only one child.')
    }
    return children[0]
  },

function renderVNodeToString (vnode, parent, context, isSvg?: boolean) {
  if (isInvalid(vnode)) {
    return ''
  }
  const { type, props, children } = vnode
  if (isVText(vnode)) {
    return encodeEntities(vnode.text)
  } else if (isVNode(vnode)) {
    let renderedString = `<${type}`
    let html
    if (!isNullOrUndef(props)) {
      for (let prop in props) {
        const value = props[prop]
        if (skipAttributes[prop]) {
          continue
        }
        if (prop === 'dangerouslySetInnerHTML') {
          html = value.__html
        } else if (prop === 'style') {
          const styleStr = renderStylesToString(value)
          renderedString += styleStr ? ` style="${renderStylesToString(value)}"` : ''
        } else if (prop === 'class' || prop === 'className') {
          renderedString += ` class="${isString(value)
            ? value
            : hashToClassName(value)}"`
        } else if (prop === 'defaultValue') {
          if (!props.value) {
            renderedString += ` value="${encodeEntities(value)}"`
          }
        } else if (prop === 'defaultChecked') {
          if (!props.checked) {
            renderedString += ` checked="${value}"`
          }
        } else if (isSvg && prop.match(/^xlink\:?(.+)/)) {
          prop = prop.toLowerCase().replace(/^xlink\:?(.+)/, 'xlink:$1')
          renderedString += ` ${prop}="${encodeEntities(value)}"`
        } else {
          if (isString(value)) {
            renderedString += ` ${prop}="${encodeEntities(value)}"`
          } else if (isNumber(value)) {
            renderedString += ` ${prop}="${value}"`
          } else if (value === true) {
            renderedString += ` ${prop}`
          }
        }
      }
    }
    if (isVoidElements[type]) {
      renderedString += `/>`
    } else {
      renderedString += `>`
      if (html) {
        renderedString += html
      } else if (!isInvalid(children)) {
        if (isString(children)) {
          renderedString += children === '' ? ' ' : encodeEntities(children)
        } else if (isNumber(children)) {
          renderedString += children + ''
        } else if (isArray(children)) {
          for (let i = 0, len = children.length; i < len; i++) {
            const child = children[i]
            if (isString(child)) {
              renderedString += child === '' ? ' ' : encodeEntities(child)
            } else if (isNumber(child)) {
              renderedString += child
            } else if (!isInvalid(child)) {
              isSvg = type === 'svg' ? true : type === 'foreignObject' ? false : isSvg
              renderedString += renderVNodeToString(
                child,
                vnode,
                context,
                isSvg
              )
            }
          }
        } else {
          isSvg = type === 'svg' ? true : type === 'foreignObject' ? false : isSvg
          renderedString += renderVNodeToString(children, vnode, context, isSvg)
        }
      }
      if (!isVoidElements[type]) {
        renderedString += `</${type}>`
      }
    }
    return renderedString
  } else if (isComposite(vnode)) {
    const instance = new type(props, context)
    instance._disable = true
    instance.props = props
    instance.context = context
    if (isFunction(instance.componentWillMount)) {
      instance.componentWillMount()
    }
    const rendered = instance.render()
    if (isFunction(instance.getChildContext)) {
      context = extend(clone(context), instance.getChildContext())
    }
    return renderVNodeToString(rendered, vnode, context, isSvg)
  } else if (isStateless(vnode)) {
    const rendered = type(props, context)
//.........这里部分代码省略.........