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component.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>
// 组件
const vnode = {
type: 'h1',
props: {
'class': 'box'
},
children: 'hello'
}
let currentInstance = null
const setCurrentInstance = () => {
}
function createRenderer() {
const hasPropsChange = (prevProps, nextProps) => { // 判断父组件前后为子组件所传递的props是否发生了变化
const nextKeys = Object.keys(nextProps)
if (nextKeys.length !== Object.keys(prevProps).length) { // 新旧props数量不等情形
return true
}
for (let i = 0; i < nextKeys.length; i++) {
const key = nextKeys[i]
if (nextProps[key] !== prevProps[key]) { //
return true
}
}
return false
}
const patchComponent = (n1, n2, anchor) => { // 组件更新
const instance = (n2.component = n1.component)
const {props} = instance
if (hasPropsChange(n1.props, n2.props)) {
const [nextProps] = resolveProps(n2.type.props, n2.props) // 获取新的props数据
for (const key in nextProps) { // 更新已有的props
props[key] = nextProps[key]
}
for (const key in props) { // 删除不存在的props
if (!(key in nextProps)) {
delete props[key]
}
}
}
}
const resolveProps = (options, propsData) => { // 解析props数据
const props = {}
const attrs = {}
for (const key in propsData) {
if (key in options || key.startsWith('on')) { // 以on开头都添加到props中去
props[key] = propsData[key]
} else {
attrs[key] = propsData[key]
}
}
return [props, attrs]
}
// 进行组件的初始渲染
const mountComponent = (vnode, container, anchor) => {
const componentOptions = vnode.type
const {render, data, setup, props: propsOption, beforeCreate, created, beforeMount, mounted, beforeUpdate, updated} = componentOptions
beforeCreate && beforeCreate()
const state = data ? reactive(data()) : null
const [props, attrs] = resolveProps(propsOption, vnode.props)
const slots = vnode.children || {}
const instance = {
state,
isMounted: false,
subTree: null,
props: shallowReactive(props),
slots
}
const emit = (event, ...payload) => {
const eventName = `on${event[0].toUpperCase() + event.slice(1)}`
const handler = instance.props[eventName]
if (handler) {
handler(...payload)
} else {
console.error('事件不存在');
}
}
// setup相关内容
const setupContext = {attrs, emit, slots}
const setupResult = setup(shallowReadonly(instance.props), setupContext)
const setupState = null
if (typeof setupResult === 'function') {
if (render) {
console.error('setup函数返回渲染函数, render选项将被忽略');
}
render = setupResult
} else {
setupState = setupResult
}
vnode.component = instance
// 创建instance的代理对象，当在渲染函数或者生命周期钩子中读取this属性值时被该对象拦截，读取或设置属性值时先从组件自身状态中进行，如果组件本身没有对应数据，再从props中数据中进行，还包括methods，computed,甚至是setupState等
const renderContext = new Proxy(instance, {
get (target, key, receiver) {
const {state, props, slots} = target
if (key === '$slots') {
return slots
}
if (state && key in state) {
return state[key]
} else if (key in props) {
return props[key]
} else if (setupState && key in setupState) { // 渲染上下文需要增加对setupState的支持
return setupState[key]
} else {
console.error('该属性不存在');
}
},
set (target, key, value, receiver) {
const {state, props} = target
if (state && key in state) {
state[key] = value
} else if (key in props) {
props[key] = value
} else if (setupState && key in setupState) { // 渲染上下文需要增加对setupState的支持
setupState[key] = value
} else {
console.error('该属性不存在');
}
}
})
created && created.call(state)
effect(() => {
const subTree = render.call(state, state)
if (!instance.isMounted) {
beforeMount && beforeMount.call(state)
patch(null, subTree, container, anchor) // 初次进行挂载
instance.isMounted = true
mounted && mounted.call(state)
} else {
beforeUpdate && beforeUpdate.call(state)
patch(instance.subTree, subTree, container, anchor)
updated && updated.call(state)
}
instance.subTree = subTree
}, {
scheduler: queueJob
})
}
const patchKeyedChildren = (n1, n2, container) => {
const oldChildren = n1.children
const newChildren = n2.children
// 更新所有前置节点
let j = 0
let oldVNode = oldChildren[j]
let newVNode = newChildren[j]
while (oldVNode.key === newVNode.key) {
// 使用while循环寻找所有相同前置节点，并进行打补丁
patch(oldVNode, newVNode, container)
j++
oldVNode = oldChildren[j]
newVNode = newChildren[j]
}
// 更新所有后置节点
let oldEnd = oldChildren.length - 1
let newEnd = newChildren.length - 1
oldVNode = oldChildren[oldEnd]
newVNode = newChildren[newEnd]
while (oldVNode.key === newVNode.key) {
patch(oldVNode, newVNode, container)
oldEnd--
newEnd--
oldVNode = oldChildren[oldEnd]
newVNode = newChildren[newEnd]
}
if (j > oldEnd && j <= newEnd) {
// 满足如下条件，说明从j-newEnd之间的节点应作为新节点进行插入
const anchorIndex = newEnd + 1 // 锚点索引
const anchor = anchorIndex < newChildren.length ? newChildren[anchorIndex].el : null
while (j <= newEnd) {
// 调用patch逐个挂载新节点
patch(null, newChildren[j++], container, anchor)
}
} else if (j > newEnd && j <= oldEnd) {
// 满足如下条件，说明从j-oldEnd之间的节点应该被进行卸载
while (j <= oldEnd) {
unmount(oldChildren[j++])
}
} else {
// 增加else分支来处理非理想情况
const count = newEnd - j + 1
const source = new Array(count)
source.fill(-1)
const oldStart = j
const newStart = j
// 两层循环嵌套有时会有性能问题
// for (let i = oldStart; i <= oldEnd; i++) {
// const oldVNode = newChildren[i]
// for (let k = newStart; k <= newEnd; k++) {
// const newVNode = newChildren[k]
// if (oldVNode.key === newVNode.key) {
// patch(oldVNode, newVNode, container)
// source[k - newStart] = i
// }
// }
// }
const moved = false
const pos = 0
const keyIndex = {}
for (let i = newStart; i < newEnd; i++) {
keyIndex[newChildren[i].key] = i
}
let patched = 0
for (let i = oldStart; i < oldEnd; i++) {
oldVNode = oldChildren[i]
if (patch < count) {
const k = keyIndex[oldVNode.key]
if (typeof k !== 'undefined') {
newVNode = newChildren[k]
patch(oldVNode, newVNode, container)
source[k - newStart] = i
patched++
if (k < pos) {
moved = true
} else {
pos = k
}
} else {
unmount(oldVNode)
}
} else {
unmount(oldVNode)
}
}
if (moved) {
// ......
}
}
}
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 === 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)
}
} else if (type === 'object') { // 组件
if (!n1) {
mountComponent(n2, container, anchor) // 挂载组件
} else {
patchComponent(n1, n2, anchor) // 更新组件
}
}
}
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>