深度了解vue.js中hooks的相关知识

export function withHooks(render) {
return {
data() {
return {
_state: {}
}
},
created() {
this._effectStore = {}
this._refsStore = {}
this._computedStore = {}
},
render(h) {
callIndex = 0
currentInstance = this
isMounting = !this._vnode
const ret = render(h, this.$attrs, this.$props)
currentInstance = null
return ret
}
}
}

export default withHooks((h)=>{
...
return <span></span>
})

const data = useData(initial)
export function useData(initial) {
const id = ++callIndex
const state = currentInstance.$data._state
if (isMounting) {
currentInstance.$set(state, id, initial)
}
return state[id]
}

const [data, setData] = useState(initial)
export function useState(initial) {
ensureCurrentInstance()
const id = ++callIndex
const state = currentInstance.$data._state
const updater = newValue => {
state[id] = newValue
}
if (isMounting) {
currentInstance.$set(state, id, initial)
}
return [state[id], updater]
}

const data = useRef(initial) // data = {current: initial}
export function useRef(initial) {
ensureCurrentInstance()
const id = ++callIndex
const { _refsStore: refs } = currentInstance
return isMounting ? (refs[id] = { current: initial }) : refs[id]
}

export default withHooks(h => {
const [count, setCount] = useState(0)
const num = useRef(count)
const log = () => {
let sum = count + 1
setCount(sum)
num.current = sum
console.log(count, num.current);
}
return (
<Button onClick={log}>{count}{num.current}</Button>
)
})

0 1
1 2
2 3
3 4
4 5

useEffect(function ()=>{
// 副作用逻辑
return ()=> {
// 清理逻辑
}
}, [deps])
export function useEffect(rawEffect, deps) {
ensureCurrentInstance()
const id = ++callIndex
if (isMounting) {
const cleanup = () => {
const { current } = cleanup
if (current) {
current()
cleanup.current = null
}
}
const effect = function() {
const { current } = effect
if (current) {
cleanup.current = current.call(this)
effect.current = null
}
}
effect.current = rawEffect
currentInstance._effectStore[id] = {
effect,
cleanup,
deps
}
currentInstance.$on('hook:mounted', effect)
currentInstance.$on('hook:destroyed', cleanup)
if (!deps || deps.length > 0) {
currentInstance.$on('hook:updated', effect)
}
} else {
const record = currentInstance._effectStore[id]
const { effect, cleanup, deps: prevDeps = [] } = record
record.deps = deps
if (!deps || deps.some((d, i) => d !== prevDeps[i])) {
cleanup()
effect.current = rawEffect
}
}
}

useMounted(function(){})
export function useMounted(fn) {
useEffect(fn, [])
}

useDestroyed(function(){})
export function useDestroyed(fn) {
useEffect(() => fn, [])
}

useUpdated(fn, deps)
export function useUpdated(fn, deps) {
const isMount = useRef(true)
useEffect(() => {
if (isMount.current) {
isMount.current = false
} else {
return fn()
}
}, deps)
}

export function useWatch(getter, cb, options) {
ensureCurrentInstance()
if (isMounting) {
currentInstance.$watch(getter, cb, options)
}
}

const data = useData({count:1})
const getCount = useComputed(()=>data.count)
export function useComputed(getter) {
ensureCurrentInstance()
const id = ++callIndex
const store = currentInstance._computedStore
if (isMounting) {
store[id] = getter()
currentInstance.$watch(getter, val => {
store[id] = val
}, { sync: true })
}
return store[id]
}

export function hooks (Vue) {
Vue.mixin({
beforeCreate() {
const { hooks, data } = this.$options
if (hooks) {
this._effectStore = {}
this._refsStore = {}
this._computedStore = {}
// 改写data函数，注入_state属性
this.$options.data = function () {
const ret = data ? data.call(this) : {}
ret._state = {}
return ret
}
}
},
beforeMount() {
const { hooks, render } = this.$options
if (hooks && render) {
// 改写组件的render函数
this.$options.render = function(h) {
callIndex = 0
currentInstance = this
isMounting = !this._vnode
// 默认传入props属性
const hookProps = hooks(this.$props)
// _self指示本身组件实例
Object.assign(this._self, hookProps)
const ret = render.call(this, h)
currentInstance = null
return ret
}
}
}
})
}

<template>
<section class="demo">
<p>{{resize}}</p>
</section>
</template>
<script>
import { hooks, useRef, useData, useState, useEffect, useMounted, useWatch } from '../hooks';
function useResize(el) {
const node = useRef(null);
const [resize, setResize] = useState({});
useEffect(
function() {
if (el) {
node.currnet = el instanceof Element ? el : document.querySelector(el);
} else {
node.currnet = document.body;
}
const Observer = new ResizeObserver(entries => {
entries.forEach(({ contentRect }) => {
setResize(contentRect);
});
});
Observer.observe(node.currnet);
return () => {
Observer.unobserve(node.currnet);
Observer.disconnect();
};
},
[]
);
return resize;
}
export default {
props: {
msg: String
},
// 这里和setup函数很接近了，都是接受props，最后返回依赖的属性
hooks(props) {
const data = useResize();
return {
resize: JSON.stringify(data)
};
}
};
</script>
<style>
html,
body {
height: 100%;
}
</style>