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diff1.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<script src="https://unpkg.com/@vue/[email protected]/dist/reactivity.global.js"></script>
</head>
<body>
<div id="app"></div>
</body>
<script>
// 双端diff算法
const vnode = {
type: 'h1',
props: {
'class': 'box'
},
children: 'hello'
}
function createRenderer() {
const patchKeyedChildren = (n1, n2, container) => {
const oldChildren = n1.children
const newChildren = n2.children
// 四个索引值
let oldStartIdx = 0
let oldEndIdx = oldChildren.length - 1
let newStartIdx = 0
let newEndIdx = newChildren.length - 1
// 四个索引值所对应的虚拟节点
let oldStartVNode = oldChildren[oldStartIdx]
let oldEndVNode = oldChildren[oldEndIdx]
let newStartVNode = newChildren[newStartIdx]
let newEndVNode = newChildren[newEndIdx]
while (oldStartIdx <= oldEndIdx && newStartIdx <= newEndIdx) {
if (!oldStartVNode) {
oldStartVNode = oldChildren[++oldStartIdx]
} else if (!oldEndVNode) {
oldEndVNode = oldChildren[--oldEndIdx]
} else if (oldStartVNode.key === newStartVNode.key) {
// 因为两者都处于头部，所以无需进行dom移动
patch(oldStartVNode, newStartVNode, container)
oldStartVNode = oldChildren[++oldStartIdx]
newStartVNode = newChildren[++newStartIdx]
} else if (oldEndVNode.key === newEndVNode.key) {
patch(oldEndVNode, newEndVNode, container)
// 因为两者都处于尾部，所以无需进行dom移动
oldEndVNode = oldChildren[--oldEndIdx]
newEndVNode = newChildren[--newEndIdx]
} else if (oldStartVNode.key === newEndVNode.key) {
patch(oldStartVNode, newEndVNode, container)
insert(oldStartVNode.el, container, oldEndVNode.el.nextSibling)
oldStartVNode = oldChildren[++oldStartIdx]
newEndVNode = newChildren[--newEndIdx]
} else if (oldEndVNode.key === newStartVNode.key) {
patch(oldEndVNode, newStartVNode, container)
insert(oldEndVNode.el, container, oldStartVNode.el) // dom移动
oldEndVNode = oldChildren[--oldEndIdx]
newStartVNode = newChildren[++newStartVNode]
} else {
// 非理想状态的处理方式
const idxInOld = oldChildren.findIndex(node => node.key === newStartVNode.key)
if (idxInOld > 0) { // 将真实dom移动到头部
const vnodeToMove = oldChildren[idxInOld]
patch(vnodeToMove, newStartVNode, container)
insert(vnodeToMove.el, container, oldStartVNode.el)
oldChildren[idxInOld] = undefined
newStartVNode = newChildren[++newStartIdx]
} else {
// 表明是新增dom, 传入锚点，进行挂载
patch(null, newStartVNode, container, oldStartVNode.el)
}
newStartVNode = newChildren[++newStartIdx]
}
}
if (oldEndIdx < oldStartIdx && newStartIdx <= newEndIdx) {
// 防止遗漏
for (let i = newStartIdx; i < newEndIdx; i++) {
patch(null, newChildren[i], container, oldStartVNode.el)
}
} else if (newEndIdx < newStartIdx && oldStartIdx <= oldEndIdx) {
// 移除不存在的元素
for (let i = oldStartIdx; i < oldEndIdx; i++) {
unmount(oldChildren[i])
}
}
}
const patchChildren = (n1, n2, container) => { // 更新children
if (typeof n2.children === 'string') { // 新子节点是文本子节点
if (Array.isArray(n1.children)) {
n1.children.forEach(c => unmount(c)) // 逐个卸载旧子节点
}
setElementText(container, n2.children)
} else if (Array.isArray(n2.children)) { // 新子节点是一组子节点
if (Array.isArray(n1.children)) {
patchKeyedChildren(n1, n2, container)
} else {
// 旧节点要么是文本子节点，要么不存在
setElementText(container, '') // 先清空容器
n2.children.forEach(c => patch(null, c, container)) // 再将新的一组子节点逐个进行挂载
}
} else {
// 新子节点不存在
if (Array.isArray(n1.children)) {
n1.children.forEach(c => unmount(c)) // 旧子节点是一组，逐个进行卸载
} else if (typeof n1.children === 'string') {
setElementText(container, '') // 旧子节点是文本，直接进行清空即可
}
}
}
const patchElement = (n1, n2) => { // 打补丁(更新)
const el = n2.el = n1.el
const oldProps = n1.props
const newProps = n2.props
// 第一步：更新这个props
for (const key in newProps) {
if (newProps[key] !== oldProps[key]) {
patchProps(el, key, oldProps[key], newProps[key])
}
}
for (const key in oldProps) {
if (!(key in newProps)) {
patchProps(el, key, oldProps[key], null)
}
}
// 第二步：更新children
patchChildren(n1, n2, el)
}
const shouldSetAsProps = (el, key) => {
// 判断dom properties是否是只读，如果是只读通过setAttribute来设置属性
if (key === 'form' && el.tagName === 'INPUT') {
return false
}
return key in el
}
const mountElement = (vnode, container, anchor) => { // 第一次挂载过程
const el = vnode.el = createElement(vnode.type) // 让vnode.el引用真实dom元素
if (vnode.props) { // 处理vnode中的props
for (const key in vnode.props) {
// el.setAttribute(key, vnode.props[key]) // 直接设置有缺陷
patchProps(el, key, null, vnode.props[key])
}
}
if (typeof vnode.children === 'string') { // 处理vnode中的children
setElementText(el, vnode.children)
} else if (Array.isArray(vnode.children)) {
vnode.children.forEach(child => {
patch(null, child, el)
})
}
insert(el, container, anchor)
}
const patch = (n1, n2, container, anchor) => {
if (n1 && n1.type !== n2.type) { //如果新旧node的type不同，直接卸载旧的node
unmount(n1)
n1 = null
}
const { type } = n2
if (type === 'string') { // 普通标签元素
if (!n1) { // 挂载
mountElement(n2, container, anchor)
} else { // 打补丁(更新)
patchElement(n1, n2)
}
} else if (type === 'object') { // 组件
} else if (type === Text) { // 文本节点
if (!n1) {
const el = n2.el = createText(n2.children)
insert(el, container)
} else {
const el = n2.el = n1.el
if (n2.children !== n1.children) {
setText(el, n2.children)
}
}
} else if (type === Fragment) { // 片段
if (!n1) {
n2.children.forEach(c => patch(null, c, container))
} else {
patchChildren(n1, n2, container)
}
}
}
const unmount = (vnode) => { // 卸载操作
if (vnode.type === Fragment) {
vnode.children.forEach(c => unmount(c))
return
}
const parent = vnode.el.parent
if (parent) parent.removeChild(vnode.el)
}
const render = (vnode, container) => {
if (vnode) {
patch(container._vnode, vnode, container) // 挂载或更新
} else {
if (container._vnode) {
// container.innerHTML = '' // 卸载，这样的卸载操作有缺陷
unmount(container._vnode)
}
}
container._vnode = vnode
}
return {
render
}
}
const renderer = createRenderer(
{
createElement(tag) {
return document.createElement(tag)
},
createText(text) {
return document.createTextNode(text)
},
setText(el, text) {
el.nodeValue = text
},
setElementText(el, text) {
el.textContent = text
},
insert(el, parent, anchor = null) {
parent.insertBefore(el, anchor)
},
patchProps(el, key, preValue, nextValue) { // 用来对dom对象上的props进行更新操作
if (/^on/.test(key)) { // 对事件进行处理
let invokers = el._vei || (el._vei = {})
const invoker = invokers[key]
const name = key.slice(2).toLowerCase()
if (nextValue) {
if (!invoker) { // 添加绑定
invoker = el._vei[key] = (e) => { // 伪造事件处理函数
if (e.timestamp < invoker.attached) return;
if (Array.isArray(invoker.value)) { // 判断同一个事件绑定多个处理函数
invoker.value.forEach(fn => fn(e))
} else {
invoker.value(e)
}
}
invoker.value = nextValue
invoker.attached = performance.now()
el.addEventListener(name, invoker)
} else { // 更新，直接更新invoker的value值即可
invoker.value = nextValue
}
} else if (invoker) { // 卸载
el.removeEventListener(name, invoker)
}
} else if (key === 'class') { // 对class做特殊处理, className的性能比setAttribute好得多
el.className = nextValue || ''
} else if (shouldSetAsProps(el, key)) {
const type = typeof el[key]
if (type === 'boolean' && nextValue === '') {
el[key] = true
} else {
el[key] = nextValue
}
} else {
el.setAttribute(key, nextValue)
}
}
}
)
renderer.render(vnode, document.getElementById('app'))
</script>
</html>