通过10个实例小练习,快速熟练 Vue3.0 核心新特性

本文来源:http://www.sg535.com/www_repian_com/

菲律宾申博代理开户合作,  “无能力补贴”的解释,看似学校撇清了自身责任。2009年9月,手机光明网上线。”但参议员舒默表示,保护当选总统是联邦政府的职责,应给予地方当局和地方警局以必要的资金补偿和帮助。

  提醒  劳动监察部门:  员工违纪罚款不得超过月薪20%  昨日下午,记者就叶先生4人被罚款远超工资一事,向南岸区劳动监察大队进行了咨询了解。要遵循思想政治工作规律,遵循教书育人规律,遵循学生成长规律,不断提高工作能力和水平。对于安倍政府如此费尽心机的安排,或许西方媒体和日本国内舆论会称颂有加,但是邻国民众却不得不带着质疑和不满看待即将上演的这出戏。要深入学习领会,自觉用讲话精神指导工作,推动高校思想政治工作和党的建设强起来。

参与联署的市议员委拉兹表示,最简单的解决办法就是请特朗普一家早点搬到华盛顿去。2011年6月,光明网直播市县委书记学习型党组织建设网上系列谈。  1月30日下午,游客何先生爆料称,在峨眉山景区雷洞坪看到一只猴子,后腿被系的绳子勒伤化脓,遇到游客便上前展示,并拉着人裤腿不放,似在求救。9日那天,得知李某的父母要到咸阳砸店时,他劝阻了但没有拦住。

Vue3.0 发 beta 版都有一段时间了,正式版也不远了,所以真的要学习一下 Vue3.0 的语法了。

GitHub 博客地址: /github_com/biaochenxuying/blog

环境搭建

$ git pull /github_com/vuejs/vue-next.git
$ cd vue-next && yarn

下载完成之后打开代码, 开启 sourceMap :

  • tsconfig.json 把 sourceMap 字段修改为 true: "sourceMap": true

  • rollup.config.js 在 rollup.config.js 中,手动键入: output.sourcemap = true

  • 生成 vue 全局的文件:yarn dev

  • 在根目录创建一个 demo 目录用于存放示例代码,并在 demo 目录下创建 html 文件,引入构建后的 vue 文件


api 的使用都是很简单的,下文的内容,看例子代码就能懂了的,所以下面的例子不会做过多解释。

reactive

reactive: 创建响应式数据对象

setup 函数是个新的入口函数,相当于 vue2.x 中 beforeCreate 和 created,在 beforeCreate 之后 created 之前执行。

<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 : 创建一个响应式的数据对象
isRef : 检查值是否是 ref 的引用对象。

<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

            /判断某值是否是响应式类型
            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 时,反应性引用和模板引用的概念是统一的。

为了获得对模板中元素或组件实例的引用,我们可以像往常一样声明 ref 并从 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 : 将响应式数据对象转换为单一响应式对象

将一个 reactive 代理对象打平,转换为 ref 代理对象,使得对象的属性可以直接在 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 : 创建计算属性

<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 的依赖项 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 : 创建 watch 监听

watchEffect : 如果响应性的属性有变更,就会触发这个函数

<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()">按钮</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:就是双向绑定

<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 函数,可以把 普通 object 对象reactive 对象ref 对象 返回一个只读对象。

返回的 readonly 对象,一旦修改就会在 consolewarning 警告。

程序还是会照常运行,不会报错。

<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

provideinject 启用类似于 2.x provide / inject 选项的依赖项注入。

两者都只能在 setup() 当前活动实例期间调用。

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 接受可选的默认值作为第二个参数。

如果未提供默认值,并且在 Provide 上下文中找不到该属性,则 inject 返回 undefined

Lifecycle Hooks

Vue2 与 Vue3 的生命周期勾子对比:

Vue2 Vue3
beforeCreate setup(替代)
created setup(替代)
beforeMount onBeforeMount
mounted onMounted
beforeUpdate onBeforeUpdate
updated onUpdated
beforeDestroy onBeforeUnmount
destroyed onUnmounted
errorCaptured onErrorCaptured
onRenderTracked
onRenderTriggered

除了 2.x 生命周期等效项之外,Composition API 还提供了以下调试挂钩:

  • onRenderTracked
  • onRenderTriggered

这两个钩子都收到一个 DebuggerEvent,类似于观察者的 onTrackonTrigger 选项:

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>

最后

笔者 GitHub 博客地址: 菲律宾申博代理开户合作/github_com/biaochenxuying/blog

本文只列出了笔者觉得会用得非常多的 api,Vue3.0 里面还有不少新特性的,比如 customRefmarkRaw ,如果读者有兴趣可看 Vue Composition API 文档。

参考文章:

支持一下下??

posted @ 2020-05-11 23:39  天明夜尽  阅读(...)  评论(...编辑  收藏
www.88sbc.com 申博官网下载登入 菲律宾申博红太阳娱乐直营网 申博游戏安卓系统下载 申愽下载直营网 www.msc99.com
申博游戏苹果手机能玩吗 www.77msc.com 菲律宾申博娱乐直营网 申博游戏登入不了 老虎机微信支付充值 申博太阳城亚洲微信支付充值
菲律宾娱乐在线网直营 申博太阳城手机版下载 申博娱乐直营网 菲律宾申博娱乐官网 申博会员登入 www.666msa.com