Vue.js Study Notes 5

Parent component passes value to child component

Component instance definition method, note: be sure to usepropsProperty to define the data passed by the parent component:

<script>
        var vm=new Vue({
            el:'#app',
            data () {
                return{
                    msg:'This is a message from the parent component'}},methods:{

            },
            components: {son: {template:' This is a child component -- {{finfo}}
'.props: ['finfo']}}});</script>
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usev-bindOr simplify instructions to pass data to child components:

<div id="app">
    <son :finfo="msg"></son>
</div>
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The code examples


      
<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>Document</title>
    <script src='https://cdn.bootcss.com/vue/2.6.10/vue.min.js'></script>
</head>

<body>
    <div id="app">
        <! When the parent can reference the child, v-bind the data we need to pass to the child to be used by the child.
        <com1 v-bind:parentmsg="msg"></com1>
    </div>

    <script>
        var vm = new Vue({
            el: '#app',
            data() {
                // The data in the child component is not passed by the parent component, but is private to the child component
                // Data is readable and writable
                return {
                    msg: '123 ah - data in parent component '
                }
            },
            methods: {

            },
            components: {
                // Conclusion: By default, the child component cannot access the data in the parent component and the methods in the parent component
                com1: {
                    template: '< h1 @ click = "change" > this is child components - {{parentmsg}} < / h1 >'.// Note that all data in the component is passed from the parent component to the child component
                    // The props data is read-only and cannot be reassigned
                    props: ['parentmsg'].// Define the parentmsg property passed by the parent component in the props array so that this data can be used
                    methods:{
                        change(){
                            this.parentmsg = "Modified."}}}},});</script>
</body>

</html>
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The parent component passes methods to the children and brings the values in the children back to the parent

The code examples


      
<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>Document</title>
    <script src='https://cdn.bootcss.com/vue/2.6.10/vue.min.js'></script>
</head>

<body>
    <div id="app">
        <! The parent component passes the method to the child component using the event binding mechanism V-ON. When we define an event attribute, the child component can somehow call the method passed in.
        <com2 @func="show"></com2>
    </div>

    <template id="tmp1">
        <div>
            <h1>This is the child component</h1>
            <input type="button" value="Here's the button on the child component, click on it to trigger the func method passed by the parent component." @click="myclick">
        </div>
    </template>

    <script>

        // Defines a component template type of literal type
        let com2 = {
            template:'#tmp1'.// Specify an Id to load the contents of the template element as the component's HTML structure
            data(){
                return {
                    sonmsg: {name:'Little head son'.age: 6}}},methods:{
                myclick(){
                    // How do I get the func method passed by the parent component and call it when I click the button of the child component?
                    // Emit; emit; emit; emit
                    this.$emit('func'.this.sonmsg)
                }
            }
        }

        var vm=new Vue({
            el:'#app',
            data () {
                return{
                    datamsgFormSon:null}},methods:{
                show(data){
                    console.log("Called show method on parent component :--" + data)
                    this.datamsgFormSon = data
                }
            },
            components:{
                com2
            }
        });
    </script>
</body>

</html>
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Build case – Comment list


      
<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>Document</title>
    <script src='https://cdn.bootcss.com/vue/2.6.10/vue.min.js'></script>
    <link href="https://cdn.bootcss.com/twitter-bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet">
</head>

<body>
    <div id="app">

        <cmt-box @func="loadComments"></cmt-box>

        <ul class="list-group">
            <li class="list-group-item" v-for="item in list" :key="item.id">
                <span class="badge">{{item.user}}</span>
                {{item.content}}
            </li>
        </ul>

    </div>

    <template id="tmp1">
        <div>
            <div class="form-group">
                <label>Comment on:</label>
                <input type="text" class="form-control" v-model="user">
            </div>

            <div class="form-group">
                <label>Comments:</label>
                <textarea class="form-control" v-model="content"></textarea>
            </div>

            <div class="form-group">
                <input type="button" value="Comment" class="btn btn-primary" @click="postComment">
            </div>
        </div>
    </template>

    <script>

        let commentBox = {
            template: '#tmp1',
            data(){
                return {
                    user:' '.content:' ',}},methods:{
                postComment(){// How to make a comment
                // Analysis: business logic for Posting comments
                //1. Where is the comment data stored?? Saved to localStorage
                //2. Organize an updated comment data object
                //3. Try to save the comment object obtained in step 2 to localStorage
                // 3.1 localStorage only supports string data, call json.stringify first
                Before saving the latest comment data, obtain the previous comment data from localStorage (string),
                // Convert to an array object and push the latest comment into the array
                // 3.3 If the comment string in localStorage is empty and does not exist, return a '[]' for json.parse to convert
                // 3.4 Convert the latest comment list array to the array string again by calling json.stringify and then calling localstorage.setitem ()
                    // this.list.push()
                    let comment = {id:Date.now, user:this.user, content:this.content}
                    // Get all comments from localStorage
                    let list = JSON.parse(localStorage.getItem('cmts') | |'[]')
                    list.unshift(comment)
                    // Re-save the latest comment data
                    localStorage.setItem('cmts'.JSON.stringify(list))
                    this.user = this.content = ' '
                    this.$emit('func')}}}var vm = new Vue({
            el: '#app',
            data() {
                return {
                    
                    list: [{id: Date.now(), user: '李白'.content: 'I was born to be useful.' },
                        { id: Date.now(), user: 'Jiang Xiao Bai'.content: 'I urge you to drink more.' },
                        { id: Date.now(), user: '小马'.content: 'My name is Ma. I'm a horse of cattle and sheep.'}}},],methods: {
                loadComments(){// Load the comment list from the local localStorage
                    let list = JSON.parse(localStorage.getItem('cmts') | |'[]')
                    this.list = list
                }
            },
            components: {
                'cmt-box': commentBox
            },
            created() {
                this.loadComments()
            },
        });
    </script>
</body>

</html>
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The final result

use`this.$refs`To get elements and components

You can invoke properties and methods in child components directly using this.$refs


      
<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>Document</title>
    <script src='https://cdn.bootcss.com/vue/2.6.10/vue.min.js'></script>
</head>

<body>
    <div id="app">
        <input type="button" value="Get elements" @click="getElement" ref="btn">
        <h3 ref='myh3'>Hahaha, what a beautiful day today!!</h3>

        <hr>
        <login ref="mylogin"></login>
    </div>


    <script>

        var login = {
            template: ' Login component 
',
            data(){
                return {
                    msg:'son msg'}},methods:{
                show(){
                    console.log('Called a child component's method')}}}var vm = new Vue({
            el: '#app',
            data() {
                return{}},methods: {
                getElement() {
                    // ref is the English word reference value type and the reference type referenceError
                    // console.log(this.$refs.myh3.innerText)
                    // console.log(this.$refs.mylogin.msg)
                    this.$refs.mylogin.show()
                }
            },
            components: {
                login
            }
        });
    </script>
</body>

</html>
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What is routing

Back-end routing: For common websites, all hyperlinks are URLS, and all urls correspond to the corresponding resources on the server.
Front-end routing: For single-page applications, the hash (#) in the URL is used to switch between different pages. The hash feature is that HTTP requests do not contain hash content. Therefore, the page jump in the single-page program is mainly implemented with hash.
In single-page applications, this way of switching pages with hash changes is called front-end routing (as opposed to back-end routing);

Use vue-router in Vue

Import vue-Router component class library

<script src="https://cdn.bootcss.com/vue-router/3.1.3/vue-router.min.js"></script>
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Use the router-link component to navigate

<! -- Router-link is rendered as an A tag by default, Use tag to change the default render tag --> <router-link to="/login"> Login </router-link> <router-link to="/register"> Register </router-link>Copy the code

Use the router-view component to display matched components

<! This element is provided by vue-Router as a placeholder for components to be displayed on the vue-Router in the future, so we can consider it as a placeholder.
<router-view></router-view>
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Create a useVueRouterCreate components

// Create a route object. After importing vue-Router, there is a route constructor called VueRouter in the window global object
        // In the new route object, can be
        const routerObj = new VueRouter({
            //route The route in this configuration object stands for route matching rule
            routes: [// Route matching rule
                // Each route is an object, a rule object, with the necessary attributes
                // Attribute 1 is path, indicating which route connection address to listen for
                // Attribute 2 is Component, which shows the component of the component attribute if the route matches the path previously
                // Note: The component property value must be a component template object, not the property name
                { path: "/login".component: login },
                { path: "/register".component: register },
            ]

        })
        
        var vm = new Vue({
            el: '#app',
            data() {
                return{}},methods: {},router:routerObj// Register the routing rule object on our VM instance to listen for URL changes and display the corresponding components
        });
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Code example to implement route default highlighting


      
<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>Document</title>
    <script src='https://cdn.bootcss.com/vue/2.6.10/vue.min.js'></script>
    <! Install vue-router routing module -->
    <script src="https://cdn.bootcss.com/vue-router/3.1.3/vue-router.min.js"></script>
    <style>
        .router-link-active..myactive{
            color: red;
            font-weight: 800;
            font-style: ittalic;
            font-size: 80px;
            text-decoration: underline;
            background-color: green;
        }
    </style>
</head>

<body>
    <div id="app">

        <! - < a href = "# / login" > login < / a > < a href = "# / register" > register < / a > -- >
        <! -- Router-link renders to an A tag by default. You can use tag to change the default render tag.
        <router-link to="/login">The login</router-link>
        <router-link to="/register">registered</router-link>

        <! This element is provided by vue-Router as a placeholder for components to be displayed on the vue-Router in the future, so we can consider it as a placeholder.
        <router-view></router-view>
    </div>

    <script>

        let login = {
            template: ' Login component 
'
        }

        let register = {
            template: ' Registered Component 
'
        }

        // Create a route object. After importing vue-Router, there is a route constructor called VueRouter in the window global object
        // In the new route object, can be
        const routerObj = new VueRouter({
            //route The route in this configuration object stands for route matching rule
            routes: [// Route matching rule
                // Each route is an object, a rule object, with the necessary attributes
                // Attribute 1 is path, indicating which route connection address to listen for
                // Attribute 2 is Component, which shows the component of the component attribute if the route matches the path previously
                // Note: The component property value must be a component template object, not the property name
                { path: "/".redirect:'/login' },Redirect and Redirect in Node are completely different things
                { path: "/login".component: login },
                { path: "/register".component: register },
            ],
            linkActiveClass:'myactive'

        })
        var vm = new Vue({
            el: '#app',
            data() {
                return{}},methods: {},router:routerObj// Register the routing rule object on our VM instance to listen for URL changes and display the corresponding components
        });
    </script>
</body>

</html>
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Add a toggle animation for the route

usetransitionThe parcelrouter-viewThe label

        <transition mode="out in">
            <router-view></router-view>
        </transition>
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Define fixed animation styles

        .v-enter..v-leave-to {
            opacity: 0;
            transform: translateX(140px);
        }

        .v-enter-active..v-laeve-active {
            transition: all 0.5 s ease;
        }
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Parameter transfer is realized in routing rules

Method 1: Use`query`To get the parameters


      
<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>Document</title>
    <script src='https://cdn.bootcss.com/vue/2.6.10/vue.min.js'></script>
    <script src="https://cdn.bootcss.com/vue-router/3.1.3/vue-router.min.js"></script>
</head>

<body>
    <div id="app">
        <! -- If you use a query string to pass parameters to a route, you do not need to modify the path attribute of the routing rule -->
        <router-link to="/login? =10&name=zs">The login</router-link>
        <router-link to="/register">registered</router-link>
        <router-view></router-view>
    </div>

    <script>

        let login = {
            template: '< h1 > login - {{$route. Query. Id}} - {{$route. The query. The name}} < / h1 >',
            created() {// The component's lifecycle hook function
                console.log(this.$route.query.id)
            },
            data(){
                return{
                    id : this.$route.query.id
                }
            }
        }

        let register = {
            template: '< h1 > register < / h1 >'
        }

        let router = new VueRouter({
            routes: [{path: '/login'.component: login },
                { path: '/register'.component: register }
            ]
        })

        var vm = new Vue({
            el: '#app',
            data() {
                return{}},methods: {

            },
            router
        });
    </script>
</body>

</html>
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Method 2: Use`params`To get the data


      
<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>Document</title>
    <script src='https://cdn.bootcss.com/vue/2.6.10/vue.min.js'></script>
    <script src="https://cdn.bootcss.com/vue-router/3.1.3/vue-router.min.js"></script>
</head>

<body>
    <div id="app">
        <! -- If you use a query string to pass parameters to a route, you do not need to modify the path attribute of the routing rule -->
        <router-link to="/login/10/lisi">The login</router-link>
        <router-link to="/register">registered</router-link>
        <router-view></router-view>
    </div>

    <script>

        let login = {
            template: '< h1 > login - {{this. $route. Params. Id}} - {{this. $route. Params. Name}} < / h1 >',
            created() {// The component's lifecycle hook function
                console.log(this.$route)
            },
            data(){
                return{
                    // id : this.$route}}}let register = {
            template: '< h1 > register < / h1 >'
        }

        let router = new VueRouter({
            routes: [{path: '/login/:id/:name'.component: login },
                { path: '/register'.component: register }
            ]
        })

        var vm = new Vue({
            el: '#app',
            data() {
                return{}},methods: {

            },
            router
        });
    </script>
</body>

</html>
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Nesting of routes

It is possible that we need to nest other routes within a route in a requirement, in which case we need to use children to nest rules


      
<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>Document</title>
    <script src='https://cdn.bootcss.com/vue/2.6.10/vue.min.js'></script>
    <script src="https://cdn.bootcss.com/vue-router/3.1.3/vue-router.min.js"></script>
</head>

<body>
    <div id="app">
        <router-link to="/account">Account</router-link>

        <router-view></router-view>
    </div>

    <template id="tmp1">
        <div>
            <h1>This is the Account component</h1>

            <router-link to="/account/login">The login</router-link>
            <router-link to="/account/register">registered</router-link>

            <router-view></router-view>
        </div>
    </template>


    <template id="tmp2">
        <div>
            <h3>This is the login component</h3>
        </div>
    </template>

    <template id="tmp3">
        <div>
            <h3>This is the registration component</h3>
        </div>
    </template>

    <script>

        // The template object of the component
        let account = {
            template: "#tmp1"
        }

        let login = {
            template: "#tmp2"
        }

        let register = {
            template: "#tmp3"
        }

        const router = new VueRouter({
            routes: [{path: '/account'.component: account,
                    // Use children to implement child routing without/before path,
                    // Otherwise, always start the request with the root path, which is inconvenient for us users to understand the URL address
                    children: [
                        { path: 'login'.component: login },
                        { path: 'register'.component: register },
                    ]
                },
                // { path: '/account/login', component: login },
                // { path: '/account/register', component: register },]})var vm = new Vue({
            el: '#app',
            data() {
                return{}},methods: {

            },
            router
        });
    </script>
</body>

</html>
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Named views implement a classic layout


      
<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>Document</title>
    <script src='https://cdn.bootcss.com/vue/2.6.10/vue.min.js'></script>
    <script src="https://cdn.bootcss.com/vue-router/3.1.3/vue-router.min.js"></script>

    <style>

        html.body{
            margin: 0;
            padding: 0;
        }

        .header{
            background-color: orange;
            height: 80px;
        }

        .left{
            background-color: lightgreen;
            flex:2
        }

        .main{
            background-color: lightpink;
            flex:8
        }

        h1{
            margin: 0;
            padding: 0;
            font-size: 16px;
        }

        .container{
            display: flex;
            height: 600px;
        }
    </style>
</head>

<body>
    <div id="app">
        <router-view></router-view>

        <div class = "container">
            <router-view name = "left"></router-view>
            <router-view name = "main"></router-view>
        </div>
    </div>

    <script>

        let header = {
            template: 'Header header 
'
        }

        let leftBox = {
            template: ' left header 
        }

        let mainBox = {
            template: ' main header 
'
        }

        // Create a routing object
        const router = new VueRouter({
            routes: [
                // {path:'/', component:header},
                // {path:'/left', component:leftBox},
                // {path:'/main', component:mainBox},

                { path: '/'.components: {
                        'default':header,
                        'left':leftBox,
                        'main':mainBox
                    } 
                },
            ]
        })

        var vm = new Vue({
            el: '#app',
            data() {
                return{}},methods: {

            },
            router
        });
    </script>
</body>

</html>
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Effect of code

Parent component passes value to child component

This is a child component -- {{finfo}}

The code examples

The parent component passes methods to the children and brings the values in the children back to the parent

The code examples

Build case – Comment list

The final result

usethis.$refsTo get elements and components

Login component

What is routing

Use vue-router in Vue

Code example to implement route default highlighting

Login component

Registered Component

Add a toggle animation for the route

Parameter transfer is realized in routing rules

Method 1: UsequeryTo get the parameters

Method 2: UseparamsTo get the data

Nesting of routes

Named views implement a classic layout

Header header

left header

main header

Effect of code

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use`this.$refs`To get elements and components

Method 1: Use`query`To get the parameters

Method 2: Use`params`To get the data