Vue3.0 發 beta 版都有一段時間了，正式版也不遠了，所以真的要學習一下 Vue3.0 的語法了。
GitHub 部落格地址: https://github.com/biaochenxuying/blog
環境搭建
$ git pull https://github.com/vuejs/vue-next.git
$ cd vue-next && yarn
下載完成之後開啟程式碼， 開啟 sourceMap :
-
tsconfig.json 把 sourceMap 欄位修改為 true:
"sourceMap": true -
rollup.config.js 在 rollup.config.js 中，手動鍵入：
output.sourcemap = true -
生成 vue 全域性的檔案：
yarn dev -
在根目錄建立一個 demo 目錄用於存放示例程式碼，並在 demo 目錄下建立 html 檔案，引入構建後的 vue 檔案
api 的使用都是很簡單的，下文的內容，看例子程式碼就能懂了的，所以下面的例子不會做過多解釋。
reactive
reactive: 建立響應式資料物件
setup 函式是個新的入口函式，相當於 vue2.x 中 beforeCreate 和 created，在
beforeCreate之後created之前執行。
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>reactive</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive } = Vue
const App = {
template: `
<button @click='click'>reverse</button>
<div style="margin-top: 20px">{{ state.message }}</div>
`,
setup() {
console.log('setup ');
const state = reactive({
message: 'Hello Vue3!!'
})
click = () => {
state.message = state.message.split('').reverse().join('')
}
return {
state,
click
}
}
}
createApp(App).mount('#app')
</script>
</html>
ref & isRef
ref : 建立一個響應式的資料物件
isRef : 檢查值是否是 ref 的引用物件。
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>ref & isRef</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, ref, isRef } = Vue
const App = {
template: `
<button @click='click'>count++</button>
<div style="margin-top: 20px">{{ count }}</div>
`,
setup() {
const count = ref(0);
console.log("count.value：", count.value) // 0
count.value++
console.log("count.value：", count.value) // 1
// 判斷某值是否是響應式型別
console.log('count is ref:', isRef(count))
click = () => {
count.value++;
console.log("click count.value：", count.value)
}
return {
count,
click,
}
}
}
createApp(App).mount('#app')
</script>
</html>
Template Refs
使用 Composition API 時，反應性引用和模板引用的概念是統一的。
為了獲得對模板中元素或元件例項的引用，我們可以像往常一樣宣告 ref 並從 setup() 返回。
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>Template Refs</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, ref, isRef, toRefs, onMounted, onBeforeUpdate } = Vue
const App = {
template: `
<button @click='click'>count++</button>
<div ref="count" style="margin-top: 20px">{{ count }}</div>
`,
setup() {
const count = ref(null);
onMounted(() => {
// the DOM element will be assigned to the ref after initial render
console.log(count.value) // <div/>
})
click = () => {
count.value++;
console.log("click count.value：", count.value)
}
return {
count,
click
}
}
}
createApp(App).mount('#app')
</script>
</html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>Template Refs</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, ref, isRef, toRefs, onMounted, onBeforeUpdate } = Vue
const App = {
template: `
<div v-for="(item, i) in list" :ref="el => { divs[i] = el }">
{{ item }}
</div>
`,
setup() {
const list = reactive([1, 2, 3])
const divs = ref([])
// make sure to reset the refs before each update
onBeforeUpdate(() => {
divs.value = []
})
onMounted(() => {
// the DOM element will be assigned to the ref after initial render
console.log(divs.value) // [<div/>]
})
return {
list,
divs
}
}
}
createApp(App).mount('#app')
</script>
</html>
toRefs
toRefs : 將響應式資料物件轉換為單一響應式物件
將一個 reactive 代理物件打平，轉換為 ref 代理物件，使得物件的屬性可以直接在 template 上使用。
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>toRefs</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, ref, isRef, toRefs } = Vue
const App = {
// template: `
// <button @click='click'>reverse</button>
// <div style="margin-top: 20px">{{ state.message }}</div>
// `,
// setup() {
// const state = reactive({
// message: 'Hello Vue3.0!!'
// })
// click = () => {
// state.message = state.message.split('').reverse().join('')
// console.log('state.message: ', state.message)
// }
// return {
// state,
// click
// }
// }
template: `
<button @click='click'>count++</button>
<div style="margin-top: 20px">{{ message }}</div>
`,
setup() {
const state = reactive({
message: 'Hello Vue3.0!!'
})
click = () => {
state.message = state.message.split('').reverse().join('')
console.log('state.message: ', state.message)
}
return {
click,
...toRefs(state)
}
}
}
createApp(App).mount('#app')
</script>
</html>
computed
computed : 建立計算屬性
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>computed</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, ref, computed } = Vue
const App = {
template: `
<button @click='handleClick'>count++</button>
<div style="margin-top: 20px">{{ count }}</div>
`,
setup() {
const refData = ref(0);
const count = computed(()=>{
return refData.value;
})
const handleClick = () =>{
refData.value += 1 // 要修改 count 的依賴項 refData
}
console.log("refData:" , refData)
return {
count,
handleClick
}
}
}
createApp(App).mount('#app')
</script>
</html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>computed</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, ref, computed } = Vue
const App = {
template: `
<button @click='handleClick'>count++</button>
<div style="margin-top: 20px">{{ count }}</div>
`,
setup() {
const refData = ref(0);
const count = computed({
get(){
return refData.value;
},
set(value){
console.log("value:", value)
refData.value = value;
}
})
const handleClick = () =>{
count.value += 1 // 直接修改 count
}
console.log(refData)
return {
count,
handleClick
}
}
}
createApp(App).mount('#app')
</script>
</html>
watch & watchEffect
watch : 建立 watch 監聽
watchEffect : 如果響應性的屬性有變更，就會觸發這個函式
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>watch && watchEffect</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, ref, watch, watchEffect } = Vue
const App = {
template: `
<div class="container">
<button style="margin-left: 10px" @click="handleClick()">按鈕</button>
<button style="margin-left: 10px" @click="handleStop">停止 watch</button>
<button style="margin-left: 10px" @click="handleStopWatchEffect">停止 watchEffect</button>
<div style="margin-top: 20px">{{ refData }}</div>
</div>`
,
setup() {
let refData = ref(0);
const handleClick = () =>{
refData.value += 1
}
const stop = watch(refData, (val, oldVal) => {
console.log('watch ', refData.value)
})
const stopWatchEffect = watchEffect(() => {
console.log('watchEffect ', refData.value)
})
const handleStop = () =>{
stop()
}
const handleStopWatchEffect = () =>{
stopWatchEffect()
}
return {
refData,
handleClick,
handleStop,
handleStopWatchEffect
}
}
}
createApp(App).mount('#app')
</script>
</html>
v-model
v-model：就是雙向繫結
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>v-model</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, watchEffect } = Vue
const App = {
template: `<button @click='click'>reverse</button>
<div></div>
<input v-model="state.message" style="margin-top: 20px" />
<div style="margin-top: 20px">{{ state.message }}</div>`,
setup() {
const state = reactive({
message:'Hello Vue 3!!'
})
watchEffect(() => {
console.log('state change ', state.message)
})
click = () => {
state.message = state.message.split('').reverse().join('')
}
return {
state,
click
}
}
}
createApp(App).mount('#app')
</script>
</html>
readonly
使用 readonly 函式，可以把 普通 object 物件、reactive 物件、ref 物件 返回一個只讀物件。
返回的 readonly 物件，一旦修改就會在 console 有 warning 警告。
程式還是會照常執行，不會報錯。
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>readonly</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, readonly, watchEffect } = Vue
const App = {
template: `
<button @click='click'>reverse</button>
<button @click='clickReadonly' style="margin-left: 20px">readonly++</button>
<div style="margin-top: 20px">{{ original.count }}</div>
`,
setup() {
const original = reactive({ count: 0 })
const copy = readonly(original)
watchEffect(() => {
// works for reactivity tracking
console.log(copy.count)
})
click = () => {
// mutating original will trigger watchers relying on the copy
original.count++
}
clickReadonly = () => {
// mutating the copy will fail and result in a warning
copy.count++ // warning!
}
return {
original,
click,
clickReadonly
}
}
}
createApp(App).mount('#app')
</script>
</html>
provide & inject
provide 和 inject 啟用類似於 2.x provide / inject 選項的依賴項注入。
兩者都只能在 setup() 當前活動例項期間呼叫。
import { provide, inject } from 'vue'
const ThemeSymbol = Symbol()
const Ancestor = {
setup() {
provide(ThemeSymbol, 'dark')
}
}
const Descendent = {
setup() {
const theme = inject(ThemeSymbol, 'light' /* optional default value */)
return {
theme
}
}
}
inject 接受可選的預設值作為第二個引數。
如果未提供預設值，並且在 Provide 上下文中找不到該屬性，則 inject 返回 undefined。
Lifecycle Hooks
Vue2 與 Vue3 的生命週期勾子對比：
| Vue2 | Vue3 |
|---|---|
| beforeCreate | setup(替代) |
| created | setup(替代) |
| beforeMount | onBeforeMount |
| mounted | onMounted |
| beforeUpdate | onBeforeUpdate |
| updated | onUpdated |
| beforeDestroy | onBeforeUnmount |
| destroyed | onUnmounted |
| errorCaptured | onErrorCaptured |
| 空 | onRenderTracked |
| 空 | onRenderTriggered |
除了 2.x 生命週期等效項之外，Composition API 還提供了以下除錯掛鉤：
onRenderTrackedonRenderTriggered
這兩個鉤子都收到一個 DebuggerEvent，類似於觀察者的 onTrack 和 onTrigger 選項：
export default {
onRenderTriggered(e) {
debugger
// inspect which dependency is causing the component to re-render
}
}
例子：
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Hello Vue3.0</title>
<style>
body,
#app {
text-align: center;
padding: 30px;
}
</style>
<script src="../../packages/vue/dist/vue.global.js"></script>
</head>
<body>
<h3>Lifecycle Hooks</h3>
<div id='app'></div>
</body>
<script>
const { createApp, reactive, onMounted, onUpdated, onUnmounted } = Vue
const App = {
template: `
<div class="container">
<button @click='click'>reverse</button>
<div style="margin-top: 20px">{{ state.message }}</div>
</div>`
,
setup() {
console.log('setup!')
const state = reactive({
message: 'Hello Vue3!!'
})
click = () => {
state.message = state.message.split('').reverse().join('')
}
onMounted(() => {
console.log('mounted!')
})
onUpdated(() => {
console.log('updated!')
})
onUnmounted(() => {
console.log('unmounted!')
})
return {
state,
click
}
}
}
createApp(App).mount('#app')
</script>
</html>
最後
筆者 GitHub 部落格地址: https://github.com/biaochenxuying/blog
本文只列出了筆者覺得會用得非常多的 api，Vue3.0 裡面還有不少新特性的，比如 customRef、markRaw ，如果讀者有興趣可看 Vue Composition API 文件。
-
Vue Composition API 文件: https://composition-api.vuejs.org/api.html#setup
-
vue-next 地址: https://github.com/vuejs/vue-next
參考文章：
支援一下下?