Get started quickly to master the new features of Vue3 core

Author : xuzhiping 2022-10-31 16:06:01 Browse: 1389

Category : JavaScript

Abstract: Get started quickly to master the new features of Vue3 core The beta version of Vue3.0 has been available for some time, and the ...

Get started quickly to master the new features of Vue3 core

The beta version of Vue3.0 has been available for some time, and the official version is not far away, so I really need to learn the grammar of Vue3.0.

GitHub blog address: https://github.com/biaochenxuying/blog.

Environment building

$ git pull https://github.com/vuejs/vue-next.git
$ cd vue-next && yarn

When the download is complete, open the code and open sourceMap:

Tsconfig.json modifies the sourceMap field to true: "sourceMap": true
Rollup.config.js in rollup.config.js, manually type: output.sourcemap = true
Generate a global file for vue: yarn dev
Create a demo directory in the root directory to store the sample code, create a html file in the demo directory, and introduce the built vue file

The use of api is very simple, the following content, look at the example code can understand, so the following examples will not explain too much.

Reactive

Reactive: creating responsive data objects.

The setup function is a new entry function, equivalent to beforeCreate and created in vue2.x, which is executed after beforeCreate and before created.

<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>

reactive

Ref & isRef

Ref: create a responsive data object isRef: check whether the value is a reference object for ref.

<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

            // Judge whether a value is a response type
            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>

ref & isRef

Template Refs

When using Composition API, the concepts of reactive reference and template reference are unified. To get a reference to the element or component instance in the template, we can declare ref as usual and return from setup ().

<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>

Template Refs not displayed

<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>

Template Refs display

ToRefs

ToRefs: convert a responsive data object to a single responsive object. Flatten a reactive proxy object and convert it to a ref proxy object, so that the properties of the object can be used directly on the template.

<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>

toRefs

Computed

Computed: creating calculation properties.

<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 // To modify the dependency of count refData
            }

            console.log("refData:" , refData)

            return {
                count,
                handleClick
            }
        }
    }
    createApp(App).mount('#app')
</script>
</html>

computed 1

<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 // directly modify count
            }

            console.log(refData)

            return {
                count, 
                handleClick
            }
        }
    }
    createApp(App).mount('#app')
</script>
</html>

computed 0

Watch & watchEffect

Watch: create watch snooping.

WatchEffect: if the responsive property changes, this function will be triggered.

<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()">button</button>
                <button style="margin-left: 10px" @click="handleStop">Stop watch</button>
                <button style="margin-left: 10px" @click="handleStopWatchEffect">Stop 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>

watch & watchEffect

V-model

V-model: bidirectional binding.

<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>

v-model

Readonly

Using the readonly function, you can return normal object objects, reactive objects, and ref objects to a read-only object.

The returned readonly object, once modified, will have a warning warning in console. The program will run as usual and will not report an error.

<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>

readonly

Provide & inject

provide and inject enable dependency injection similar to the 2.x provide / inject option. Both can only be called during the current active instance of setup().

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 accepts the optional default value as the second parameter.

If no default value is provided and the property cannot be found in the Provide context, inject returns undefined.

Lifecycle Hooks

Comparison of life cycle hooks between Vue2 and Vue3:

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

In addition to 2. x lifecycle equivalents, the Composition API also provides the following debugging hooks:

onRenderTracked
onRenderTriggered

Both hooks receive a DebuggerEvent, onTrack and onTrigger similar to observers:

export default {
  onRenderTriggered(e) {
    debugger
    // inspect which dependency is causing the component to re-render
  }
}

Example：

<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>

Lifecycle Hooks

Last

This article only lists the api,Vue3.0 that the author thinks will be used a lot, and there are many new features in it, such as customRef, markRaw. If readers are interested, you can read the Vue Composition API documentation.

Vue Composition API documents: https://composition-api.vuejs.org/api.html#setup

Vue-next address: https://github.com/vuejs/vue-next

Label : Vue3

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