页面渲染时调用patch方法,将新旧vnode进行比较(diff算法),映射成实际DOM。
页面渲染时调用patch方法,将新旧vnode进行比较(diff算法),映射成实际DOM。
# createElm方法
创建VNode节点的vnode. elm
- createComponent的作用是在创建组件实例(init钩子生成),初始化(initComponent方法初始化)并激活组件(insert方法激活)
- createChildren创建子节点,子节点为数组时循环调用createElm
function createElm(vnode, insertedVnodeQueue, parentElm, refElm, nested) {
// 创建一个组件节点
if (createComponent(vnode, insertedVnodeQueue, parentElm, refElm)) {
return
}
const data = vnode.data;
const childre = vnode.children;
const tag = vnode.tag;
// ...
if (isDef(tag)) {
vnode.elm = vnode.ns ?
nodeOps.createElementNS(vnode.ns, tag) :
nodeOps.createElement(tag, vnode)
setScope(vnode)
if (isDef(data)) {
invokeCreateHooks(vnode, insertedVnodeQueue)
}
createChildren(vnode, children, insertedVnodeQueue)
} else if (isTrue(vnode.isComment)) {
vnode.elm = nodeOps.createComment(vnode.text);
} else {
vnode.elm = nodeOps.createTextNode(vnode.te)
}
insert(parentElm, vnode.elm, refElm)
}
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
# sameVnode方法
判断两个节点是否相同
- key相同
- tag标签类型相同
- isComment注释节点标示相同(都为注释节点或者都不为注释节点)
- data值状态相同
- 或者是存在异步占位符,异步工厂方法且报错的情况
- sameInputType方法判断input的type相同
- isDef判断是否为null/undefined
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)
)
)
)
}
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
# patch方法
创建节点的过程是放入队列中统一处理 createComponent(会判断是否有children然后递归调用) createComment createTextNode
return function patch(oldVnode, vnode, hydrating, removeOnly) {
if (isUndef(vnode)) {
if (isDef(oldVnode)) invokeDestroyHook(oldVnode)
return
}
let isInitialPatch = false
const insertedVnodeQueue = []
if (isUndef(oldVnode)) {
// empty mount (likely as component), create new root element
isInitialPatch = true
createElm(vnode, insertedVnodeQueue)
} else {
const isRealElement = isDef(oldVnode.nodeType)
if (!isRealElement && sameVnode(oldVnode, vnode)) {
// patch existing root node
patchVnode(oldVnode, vnode, insertedVnodeQueue, null, null, removeOnly)
} else {
if (isRealElement) {
// mounting to a real element
// check if this is server-rendered content and if we can perform
// a successful hydration.
if (oldVnode.nodeType === 1 && oldVnode.hasAttribute(SSR_ATTR)) {
oldVnode.removeAttribute(SSR_ATTR)
hydrating = true
}
if (isTrue(hydrating)) {
if (hydrate(oldVnode, vnode, insertedVnodeQueue)) {
invokeInsertHook(vnode, insertedVnodeQueue, true)
return oldVnode
} else if (process.env.NODE_ENV !== 'production') {
warn(
'The client-side rendered virtual DOM tree is not matching ' +
'server-rendered content. This is likely caused by incorrect ' +
'HTML markup, for example nesting block-level elements inside ' +
'<p>, or missing <tbody>. Bailing hydration and performing ' +
'full client-side render.'
)
}
}
// either not server-rendered, or hydration failed.
// create an empty node and replace it
oldVnode = emptyNodeAt(oldVnode)
}
// replacing existing element
const oldElm = oldVnode.elm
const parentElm = nodeOps.parentNode(oldElm)
// create new node
createElm(
vnode,
insertedVnodeQueue,
// extremely rare edge case: do not insert if old element is in a
// leaving transition. Only happens when combining transition +
// keep-alive + HOCs. (#4590)
oldElm._leaveCb ? null : parentElm,
nodeOps.nextSibling(oldElm)
)
// update parent placeholder node element, recursively
if (isDef(vnode.parent)) {
let ancestor = vnode.parent
const patchable = isPatchable(vnode)
while (ancestor) {
for (let i = 0; i < cbs.destroy.length; ++i) {
cbs.destroy[i](ancestor)
}
ancestor.elm = vnode.elm
if (patchable) {
for (let i = 0; i < cbs.create.length; ++i) {
cbs.create[i](emptyNode, ancestor)
}
// #6513
// invoke insert hooks that may have been merged by create hooks.
// e.g. for directives that uses the "inserted" hook.
const insert = ancestor.data.hook.insert
if (insert.merged) {
// start at index 1 to avoid re-invoking component mounted hook
for (let i = 1; i < insert.fns.length; i++) {
insert.fns[i]()
}
}
} else {
registerRef(ancestor)
}
ancestor = ancestor.parent
}
}
// destroy old node
if (isDef(parentElm)) {
removeVnodes([oldVnode], 0, 0)
} else if (isDef(oldVnode.tag)) {
invokeDestroyHook(oldVnode)
}
}
}
invokeInsertHook(vnode, insertedVnodeQueue, isInitialPatch)
return vnode.elm
}
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
# patchVnode方法
当两个节点相同时执行patchVnode方法。将旧节点的属性赋值给新节点的elm属性
function patchVnode(
oldVnode,
vnode,
insertedVnodeQueue,
ownerArray,
index,
removeOnly
) {
// 1. 如果新旧节点完全相同(引用相同 oldVnode === vnode)直接返回不处理
if (oldVnode === vnode) {
return
}
if (isDef(vnode.elm) && isDef(ownerArray)) {
// clone reused vnode
vnode = ownerArray[index] = cloneVNode(vnode)
}
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
}
// reuse element for static trees.
// note we only do this if the vnode is cloned -
// if the new node is not cloned it means the render functions have been
// reset by the hot-reload-api and we need to do a proper re-render.
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)
}
// 2. 新节点不是文本节点
if (isUndef(vnode.text)) {
// 2-1. 都存在子节点,新旧节点的子节点数组引用不同(oldCh !== ch)调用updateChildren
if (isDef(oldCh) && isDef(ch)) {
if (oldCh !== ch) updateChildren(elm, oldCh, ch, insertedVnodeQueue, removeOnly)
} else if (isDef(ch)) { // 2-1. 新节点有子节点,旧节点没有
// 2-2-1. 查子节点key
if (process.env.NODE_ENV !== 'production') {
checkDuplicateKeys(ch)
}
// 2-2-2. 旧节点为文本节点时先清空文本
if (isDef(oldVnode.text)) nodeOps.setTextContent(elm, '')
// 2-2-3.创建子节点DOM元素
addVnodes(elm, null, ch, 0, ch.length - 1, insertedVnodeQueue)
} else if (isDef(oldCh)) {
// 2-3. 旧节点有子节点,新节点无时移除子节点和dom
removeVnodes(oldCh, 0, oldCh.length - 1)
} else if (isDef(oldVnode.text)) {
// 2-4. 新节点是文本时直接替换文本内容
nodeOps.setTextContent(elm, '')
}
} else if (oldVnode.text !== vnode.text) {
// 3. 都是文本节点则替换文字
nodeOps.setTextContent(elm, vnode.text)
}
if (isDef(data)) {
if (isDef(i = data.hook) && isDef(i = i.postpatch)) i(oldVnode, vnode)
}
}
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
# updateChildren方法(diff)
diff算法的比较是同层比较(广度优先),当节点不同时会直接删掉。节省掉很多比较的时间 处理相同新旧节点的子节点。相当于新旧节点的头尾都有一个指针(共四个),对比过程以新起始节点为主导,右两侧往中间进行比较。
旧子节点存在undefined节点
- 起始undefined,oldStartVnode = oldCh[++oldStartIdx]
- 结尾undefined,oldEndVnode = oldCh[--oldStartIdx]
新旧子节点的起始节点相同: patchVnode更新内容,并且两个起始指针往后延1
新旧子节点的结尾节点相同: patchVnode更新内容,并且两个结尾指针往前延1
新结尾与旧起始相同: patchVnode更新内容,将旧起始节点DOM加到旧结尾DOM前面,旧起始往后,新结尾往前
新起始与旧结尾相同: patchVnode更新内容,将旧结尾节点DOM加到旧结开始DOM前面,旧结尾往前,新其实往后
其他
- 和新其实节点都不同:创建新节点DOM并且添加到旧起始DOM前面
- 存在于新其实key相同,标签相同:patchVnode,旧节点添加到旧起始DOM前,再置为undefined
- key相同标签类型不同:创建新节点并添加到旧起始节点DOM前
循环结束如果oldStartIdx>oldEndIdx:将剩余未处理新节点DOM添加到上个新结尾节点前
oldStartIdx<oldEndIdx: 移除旧节点和DOM
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
// removeOnly is a special flag used only by <transition-group>
// to ensure removed elements stay in correct relative positions
// during leaving transitions
const canMove = !removeOnly
if (process.env.NODE_ENV !== 'production') {
checkDuplicateKeys(newCh)
}
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, newCh, newStartIdx)
oldStartVnode = oldCh[++oldStartIdx]
newStartVnode = newCh[++newStartIdx]
} else if (sameVnode(oldEndVnode, newEndVnode)) {
patchVnode(oldEndVnode, newEndVnode, insertedVnodeQueue, newCh, newEndIdx)
oldEndVnode = oldCh[--oldEndIdx]
newEndVnode = newCh[--newEndIdx]
} else if (sameVnode(oldStartVnode, newEndVnode)) { // Vnode moved right
patchVnode(oldStartVnode, newEndVnode, insertedVnodeQueue, newCh, newEndIdx)
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, newCh, newStartIdx)
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, newCh, newStartIdx)
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(oldCh, oldStartIdx, oldEndIdx)
}
}
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
# 实例
# 例子
- 左边表示新旧节点,节点下面标识起始和结尾节点(即正在处理的节点)。右边表示当前的DOM。
- 新节点的起始和结尾节点与旧节点的起始和结尾节点互不相同,并且在旧节点中未找到与新起始节点(新节点f)相同的节点。
所以创建节点f的DOM并添加到旧起始节点(旧节点a)DOM的前面,然后新起始节点序号加1,表示新节点f已处理,当前正在处理新起始节点c。
- 新节点的起始和结尾节点与旧节点的起始和结尾节点互不相同,但在旧节点中找到与新起始节点(节点c)相同的节点。
所以将旧节点c的DOM添加到旧起始节点(旧节点a)DOM的前面,旧节点c置空,然后新起始节点序号加1,表示新节点c已处理,当前正在处理新起始节点e。
- 新起始节点(新节点e)和旧结尾节点(旧节点e)相同。更新旧节点e的DOM内容,并将旧节点e的DOM移动到旧起始节点(旧节点a)DOM的前面,旧结尾节点序号减1,新起始节点加1,表示新旧节点e已处理,当前正在处理的是新起始节点g和旧结尾节点d。
- 新结尾节点(新节点d)和旧结尾节点(旧节点d)相同。仅更新旧节点d的DOM内容。新结尾节点序号减1,旧结尾节点序号减1,表示新旧节点d已处理,当前正在处理的是新结尾节点g和旧结尾节点c。由于旧节点c为空,则旧结尾节点为b。
- 新节点的起始和结尾节点与旧节点的起始和结尾节点互不相同,并且在旧节点中未找到与新起始节点(新节点g)相同的节点。
所以创建节点g的DOM并添加到旧起始节点(旧节点a)DOM的前面,然后新起始节点序号加1,表示新节点g已处理,当前正在处理新起始节点d。
- 由于新起始和结尾节点序号重叠,新节点已经处理完毕,存在尚未处理的旧节点,则移除未处理的旧节点DOM。
- 结束,最终的DOM。