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vue依赖收集.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Vue 依赖收集</title>
</head>
<style type="text/css">
</style>
<body>
<script>
class Dep {
constructor() {
this.deps = []
}
depend() {
if (Dep.target && this.deps.indexOf(Dep.target) === -1) {
this.deps.push(Dep.target)
}
}
notify() {
this.deps.forEach((dep) => {
dep()
})
}
}
Dep.target = null
// 同样的道理，我们对observable和watcher都进行一定的封装与优化，使这个响应式系统变得模块化：
class Observable {
constructor(obj) {
return this.walk(obj)
}
walk(obj) {
const keys = Object.keys(obj)
keys.forEach((key) => {
this.defineReactive(obj, key, obj[key])
})
return obj
}
defineReactive(obj, key, val) {
const dep = new Dep()
Object.defineProperty(obj, key, {
get() {
dep.depend()
return val
},
set(newVal) {
val = newVal
dep.notify()
}
})
}
}
class Watcher {
constructor(obj, key, cb, onComputedUpdate) {
this.obj = obj
this.key = key
this.cb = cb
this.onComputedUpdate = onComputedUpdate
return this.defineComputed()
}
defineComputed() {
const self = this
const onDepUpdated = () => {
const val = self.cb()
this.onComputedUpdate(val)
}
Object.defineProperty(self.obj, self.key, {
get() {
Dep.target = onDepUpdated
const val = self.cb()
Dep.target = null
return val
},
set() {
console.error('计算属性无法被赋值！')
}
})
}
}
// 然后我们来跑一下：
const hero = new Observable({
health: 3000,
IQ: 150
})
new Watcher(hero, 'type', () => {
return hero.health > 4000 ? '坦克' : '脆皮'
}, (val) => {
console.log(`我的类型是：${val}`)
})
console.log(`英雄初始类型：${hero.type}`)
hero.health = 5000
// -> 英雄初始类型：脆皮
// -> 我的类型是：坦克
// https://www.cnblogs.com/ajianbeyourself/p/8962813.html
</script>
</body>
</html>