假造dom
diff算法起首要明白一个观点就是diff的对象是假造dom，更新实在dom则是diff算法的效果
Vnode基类
constructor (
。。。
) {
this.tag = tag
this.data = data
this.children = children
this.text = text
this.elm = elm
this.ns = undefined
this.context = context
this.fnContext = undefined
this.fnOptions = undefined
this.fnScopeId = undefined
this.key = data && data.key
this.componentOptions = componentOptions
this.componentInstance = undefined
this.parent = undefined
this.raw = false
this.isStatic = false
this.isRootInsert = true
this.isComment = false
this.isCloned = false
this.isOnce = false
this.asyncFactory = asyncFactory
this.asyncMeta = undefined
this.isAsyncPlaceholder = false
}这个部份的代码 重假如为了更好地晓得在diff算法中详细diff的属性的寄义，固然也能够更好地相识vnode实例
团体历程
中心函数是patch函数
- isUndef推断（是不是是undefined或许null）
- // empty mount (likely as component), create new root elementcreateElm(vnode, insertedVnodeQueue) 这里能够发明建立节点不是一个一个插进去，而是放入一个行列中统一批处置惩罚
- 中心函数sameVnode
function sameVnode (a, b) {
return (
a.key === b.key && (
(
a.tag === b.tag &&
a.isComment === b.isComment &&
isDef(a.data) === isDef(b.data) &&
sameInputType(a, b)
) || (
isTrue(a.isAsyncPlaceholder) &&
a.asyncFactory === b.asyncFactory &&
isUndef(b.asyncFactory.error)
)
)
)
}这里是一个外层的比较函数，直接去比较了两个节点的key，tag（标签）,data的比较（注重这里的data指的是VNodeData），input的话直接比较type。
export interface VNodeData {
key?: string | number;
slot?: string;
scopedSlots?: { [key: string]: ScopedSlot };
ref?: string;
tag?: string;
staticClass?: string;
class?: any;
staticStyle?: { [key: string]: any };
style?: object[] | object;
props?: { [key: string]: any };
attrs?: { [key: string]: any };
domProps?: { [key: string]: any };
hook?: { [key: string]: Function };
on?: { [key: string]: Function | Function[] };
nativeOn?: { [key: string]: Function | Function[] };
transition?: object;
show?: boolean;
inlineTemplate?: {
render: Function;
staticRenderFns: Function[];
};
directives?: VNodeDirective[];
keepAlive?: boolean;
}这会确认两个节点是不是有进一步比较的代价，不然直接替代
替代的历程重假如一个createElm函数 别的则是烧毁oldVNode
// destroy old node
if (isDef(parentElm)) {
removeVnodes(parentElm, [oldVnode], 0, 0)
} else if (isDef(oldVnode.tag)) {
invokeDestroyHook(oldVnode)
}插进去历程简化来讲就是推断node的type离别挪用
createComponent（会推断是不是有children然后递归挪用）
createComment
createTextNode
建立后运用insert函数
以后需要用hydrate函数将假造dom和真是dom举行映照
function insert (parent, elm, ref) {
if (isDef(parent)) {
if (isDef(ref)) {
if (ref.parentNode === parent) {
nodeOps.insertBefore(parent, elm, ref)
}
} else {
nodeOps.appendChild(parent, elm)
}
}
}中心函数
function patchVnode (oldVnode, vnode, insertedVnodeQueue, removeOnly) {
if (oldVnode === vnode) {
return
}
const elm = vnode.elm = oldVnode.elm
if (isTrue(oldVnode.isAsyncPlaceholder)) {
if (isDef(vnode.asyncFactory.resolved)) {
hydrate(oldVnode.elm, vnode, insertedVnodeQueue)
} else {
vnode.isAsyncPlaceholder = true
}
return
}
if (isTrue(vnode.isStatic) &&
isTrue(oldVnode.isStatic) &&
vnode.key === oldVnode.key &&
(isTrue(vnode.isCloned) || isTrue(vnode.isOnce))
) {
vnode.componentInstance = oldVnode.componentInstance
return
}
let i
const data = vnode.data
if (isDef(data) && isDef(i = data.hook) && isDef(i = i.prepatch)) {
i(oldVnode, vnode)
}
const oldCh = oldVnode.children
const ch = vnode.children
if (isDef(data) && isPatchable(vnode)) {
for (i = 0; i < cbs.update.length; ++i) cbs.update[i](oldVnode, vnode)
if (isDef(i = data.hook) && isDef(i = i.update)) i(oldVnode, vnode)
}
if (isUndef(vnode.text)) {
if (isDef(oldCh) && isDef(ch)) {
if (oldCh !== ch) updateChildren(elm, oldCh, ch, insertedVnodeQueue, removeOnly)
} else if (isDef(ch)) {
if (isDef(oldVnode.text)) nodeOps.setTextContent(elm, '')
addVnodes(elm, null, ch, 0, ch.length - 1, insertedVnodeQueue)
} else if (isDef(oldCh)) {
removeVnodes(elm, oldCh, 0, oldCh.length - 1)
} else if (isDef(oldVnode.text)) {
nodeOps.setTextContent(elm, '')
}
} else if (oldVnode.text !== vnode.text) {
nodeOps.setTextContent(elm, vnode.text)
}
if (isDef(data)) {
if (isDef(i = data.hook) && isDef(i = i.postpatch)) i(oldVnode, vnode)
}
}const el = vnode.el = oldVnode.el 这是很主要的一步，让vnode.el援用到现在的实在dom，当el修改时，vnode.el会同步变化。
- 比较两者援用是不是一致
- 以后asyncFactory不晓得是做什么的，所以这个比较看不懂
- 静态节点比较key，雷同后也不做从新衬着，直接拷贝componentInstance（once敕令在此见效）
- 假如vnode是文本节点或解释节点，然则vnode.text != oldVnode.text时，只需要更新vnode.elm的文本内容就能够
children的比较
- 假如只要oldVnode有子节点，那就把这些节点都删除
- 假如只要vnode有子节点，那就建立这些子节点，这里假如oldVnode是个文本节点就把vnode.elm的文本设置为空字符串
- 都有则updateChildren，这个以后详述
- 假如oldVnode和vnode都没有子节点，然则oldVnode是文本节点或解释节点，就把vnode.elm的文本设置为空字符串
updateChildren
这部份重点照样关注全部算法
起首四个指针，oldStart，oldEnd，newStart，newEnd，两个数组，oldVnode，Vnode。
function updateChildren (parentElm, oldCh, newCh, insertedVnodeQueue, removeOnly) {
let oldStartIdx = 0
let newStartIdx = 0
let oldEndIdx = oldCh.length - 1
let oldStartVnode = oldCh[0]
let oldEndVnode = oldCh[oldEndIdx]
let newEndIdx = newCh.length - 1
let newStartVnode = newCh[0]
let newEndVnode = newCh[newEndIdx]
let oldKeyToIdx, idxInOld, vnodeToMove, refElm
while (oldStartIdx <= oldEndIdx && newStartIdx <= newEndIdx) {
if (isUndef(oldStartVnode)) {
oldStartVnode = oldCh[++oldStartIdx] // Vnode has been moved left
} else if (isUndef(oldEndVnode)) {
oldEndVnode = oldCh[--oldEndIdx]
} else if (sameVnode(oldStartVnode, newStartVnode)) {
patchVnode(oldStartVnode, newStartVnode, insertedVnodeQueue)
oldStartVnode = oldCh[++oldStartIdx]
newStartVnode = newCh[++newStartIdx]
} else if (sameVnode(oldEndVnode, newEndVnode)) {
patchVnode(oldEndVnode, newEndVnode, insertedVnodeQueue)
oldEndVnode = oldCh[--oldEndIdx]
newEndVnode = newCh[--newEndIdx]
} else if (sameVnode(oldStartVnode, newEndVnode)) { // Vnode moved right
patchVnode(oldStartVnode, newEndVnode, insertedVnodeQueue)
canMove && nodeOps.insertBefore(parentElm, oldStartVnode.elm, nodeOps.nextSibling(oldEndVnode.elm))
oldStartVnode = oldCh[++oldStartIdx]
newEndVnode = newCh[--newEndIdx]
} else if (sameVnode(oldEndVnode, newStartVnode)) { // Vnode moved left
patchVnode(oldEndVnode, newStartVnode, insertedVnodeQueue)
canMove && nodeOps.insertBefore(parentElm, oldEndVnode.elm, oldStartVnode.elm)
oldEndVnode = oldCh[--oldEndIdx]
newStartVnode = newCh[++newStartIdx]
} else {
if (isUndef(oldKeyToIdx)) oldKeyToIdx = createKeyToOldIdx(oldCh, oldStartIdx, oldEndIdx)
idxInOld = isDef(newStartVnode.key)
? oldKeyToIdx[newStartVnode.key]
: findIdxInOld(newStartVnode, oldCh, oldStartIdx, oldEndIdx)
if (isUndef(idxInOld)) { // New element
createElm(newStartVnode, insertedVnodeQueue, parentElm, oldStartVnode.elm, false, newCh, newStartIdx)
} else {
vnodeToMove = oldCh[idxInOld]
if (sameVnode(vnodeToMove, newStartVnode)) {
patchVnode(vnodeToMove, newStartVnode, insertedVnodeQueue)
oldCh[idxInOld] = undefined
canMove && nodeOps.insertBefore(parentElm, vnodeToMove.elm, oldStartVnode.elm)
} else {
// same key but different element. treat as new element
createElm(newStartVnode, insertedVnodeQueue, parentElm, oldStartVnode.elm, false, newCh, newStartIdx)
}
}
newStartVnode = newCh[++newStartIdx]
}
}
if (oldStartIdx > oldEndIdx) {
refElm = isUndef(newCh[newEndIdx + 1]) ? null : newCh[newEndIdx + 1].elm
addVnodes(parentElm, refElm, newCh, newStartIdx, newEndIdx, insertedVnodeQueue)
} else if (newStartIdx > newEndIdx) {
removeVnodes(parentElm, oldCh, oldStartIdx, oldEndIdx)
}
}一个轮回比较的几种状况和处置惩罚（以下的++ –均指index的++ –）比较则是比较的node节点，简朴写法 不严谨 比较用的是sameVnode函数也不是真的全等
团体轮回不完毕的前提oldStartIdx <= oldEndIdx && newStartIdx <= newEndIdx
- oldStart === newStart，oldStart++ newStart++
- oldEnd === newEnd，oldEnd– newEnd–
- oldStart === newEnd, oldStart插到部队末端 oldStart++ newEnd–
- oldEnd === newStart, oldEnd插到部队开首 oldEnd– newStart++
剩下的一切状况都走这个处置惩罚简朴的说也就两种处置惩罚，处置惩罚后newStart++
- newStart在old中发明一样的那末将这个移动到oldStart前
- 没有发明一样的那末建立一个放到oldStart之前
轮回完毕后并没有完成
另有一段推断才算完
if (oldStartIdx > oldEndIdx) {
refElm = isUndef(newCh[newEndIdx + 1]) ? null : newCh[newEndIdx + 1].elm
addVnodes(parentElm, refElm, newCh, newStartIdx, newEndIdx, insertedVnodeQueue)
} else if (newStartIdx > newEndIdx) {
removeVnodes(parentElm, oldCh, oldStartIdx, oldEndIdx)
}简朴的说就是轮回完毕后，看四个指针中心的内容，old数组中和new数组中，多退少补罢了
总结
团体熟悉还很粗拙，不过以现在的水温和对vue的相识也就只能到这了
