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| <div id="app"></div>
<script>
function h(tag, props, children) {
return { tag, props, children }
}
function mount(vnode, container) {
const el = (vnode.el = document.createElement(vnode.tag))
if (vnode.props) {
for (const key in vnode.props) {
const value = vnode.props[key]
if (key.startsWith("on")) {
el.addEventListener(key.slice(2).toLowerCase(), value)
} else {
el.setAttribute(key, value)
}
}
}
if (vnode.children) {
if (typeof vnode.children === "string") {
el.textContent = vnode.children
} else {
vnode.children.forEach((child) => {
mount(child, el)
})
}
}
container.appendChild(el)
}
function patch(n1, n2) {
if (n1.tag === n2.tag) {
const el = (n2.el = n1.el)
const oldProps = n1.props || {}
const newProps = n2.props || {}
for (const key in newProps) {
const oldVal = oldProps[key]
const newVal = newProps[key]
if (newVal !== oldVal) {
el.setAttribute(key, newVal)
}
}
for (const key in oldProps) {
if (!(key in newProps)) {
el.removeAttribute(key)
}
}
const oldChildren = n1.children
const newChildren = n2.children
if (typeof newChildren === "string") {
if (typeof oldChildren === "string") {
if (newChildren !== oldChildren) {
el.textContent = newChildren
}
} else {
el.textContent = newChildren
}
} else {
if (typeof oldChildren === "string") {
el.innerHTML = ""
newChildren.forEach((child) => {
mount(child, el)
})
} else {
const commonLength = Math.min(oldChildren.length, newChildren.length)
for (let i = 0; i < commonLength; i++) {
patch(oldChildren[i], newChildren[i])
}
if (newChildren.length > oldChildren.length) {
newChildren.slice(oldChildren.length).forEach((child) => {
mount(child, el)
})
}
if (newChildren.length < oldChildren.length) {
oldChildren.slice(newChildren.length).forEach((child) => {
el.removeChild(child.el)
})
}
}
}
} else {
}
}
let activeEffect
class Dep {
subscribers = new Set()
depend() {
if (activeEffect) {
this.subscribers.add(activeEffect)
}
}
notify() {
this.subscribers.forEach((effect) => {
effect()
})
}
}
function watchEffect(effect) {
activeEffect = effect
effect()
activeEffect = null
}
const targetMap = new WeakMap()
function getDep(target, key) {
let depsMap = targetMap.get(target)
if (!depsMap) {
depsMap = new Map()
targetMap.set(target, depsMap)
}
let dep = depsMap.get(key)
if (!dep) {
dep = new Dep()
depsMap.set(key, dep)
}
return dep
}
const reactiveHandlers = {
get(target, key, receiver) {
const dep = getDep(target, key)
dep.depend()
return Reflect.get(target, key, receiver)
},
set(target, key, value, receiver) {
const dep = getDep(target, key)
const result = Reflect.set(target, key, value, receiver)
dep.notify()
return result
},
}
function reactive(raw) {
return new Proxy(raw, reactiveHandlers)
}
const App = {
data: reactive({
count: 22,
}),
render() {
return h(
"div",
{
onClick: () => {
this.data.count++
},
},
String(this.data.count)
)
},
}
function mountApp(component, container) {
let isMounted = false
let prevVdom
watchEffect(() => {
if (!isMounted) {
prevVdom = component.render()
mount(prevVdom, container)
isMounted = true
} else {
const newVdom = component.render()
patch(prevVdom, newVdom)
prevVdom = newVdom
}
})
}
mountApp(App, document.getElementById("app"))
</script>
|
