What is the difference between vuejs2 and 1

Differences: 1. When using the v-for instruction in vue2, you can add repeated content, but vue1 cannot; 2. vue2 has filters, but vue1 does not; 3. The communication methods between components are different; 4. The life cycle is different etc.

The operating environment of this tutorial: windows7 system, vue2.9.6 version, DELL G3 computer.

Difference 1:

When using the v-for directive in vue2, it can add repeated content, just like you can add The same message content, let’s take a look at

When writing code, the first thing to import is the vue2js file.

HTML code:

<div id="box">
        <input type="button" value="添加" @click="add()">
        <ul>
            <li v-for="item in arr">{{item}}</li>
        </ul>
    </div>

JS code:

window.onload=function () {
           new Vue({
               el:"#box",
               data:{
                  arr:[1,2,3,4,5,6]
               },
               methods: {
                   add:function () {
                       this.arr.unshift("1")
                   }
               }
           })
       }

However, there is another difference, that is, there is no $index. There is in vue1, but we can Manually add $index

<div id="box">
        <input type="button" value="添加" @click="add()">
        <ul>
            <li v-for="(val,index) in arr">{{val}}------->{{index}}</li>
        </ul>
    </div>

Difference 2:

We have a big difference between vue2 and vue1 that there is no filter! ! ! When we use filters, we have to define them ourselves.

Difference 3:

Furthermore, we use communication between components differently. Let’s take a look at it below:

HTML code:

<div id="div">
    我是父组件---->{{emitData.msg}}<br>
    <child-com :m="emitData"></child-com>
</div>
</body>
</html>
<template id="tpl">
    <div>
        <span>我是子组件----></span>
        {{m.msg}}<br>
        <input type="button" value="change" @click="change()"/>
    </div>
</template>

JS code:

window.onload = function(){
       new Vue({
           el:"#div",
           data:{
               emitData:{  //写为json 原理：js中对象的引用
                   msg:"我是父组件数据"
               }
           },
           components:{
               'child-com':{
                   props:['m'],
                   template:"#tpl",
                   methods:{
                       change(){
                           this.m.msg='变了';
                       }
                   }
               }
           }
       })
   }

This is not a method in vue2 but we can use this method to solve the problem.

Difference 4:

One of the most basic differences is that when we define a template, we should wrap the template in a big box.

<template id="tpl">
    <div><h3>3333333</h3><strong>strong</strong></div>
</template>

Difference 5:

The life cycle is also different. The life cycle in our vue2 is like this

window.onload=function () {
           new Vue({
               el:"#box",
               data:{
                   msg:"lalalal"
               },
               beforeCreate () {
                   alert("实例创建之前")
               },
               created() {
                   alert("实例创建完成")
               },
               beforeMount() {
                   alert("数据编译之前")
               },
               mounted() {
                   alert("数据编译完成")
               },
               beforeUpdate:function () {
                   console.log("数据更新之前")
               },
               updated:function () {
                   console.log("数据解析完成")
               },
               beforeDestroy:function () {
                   alert("数据销毁之前")
               },
               destroyed:function () {
                   alert("数据销毁完成")
               }
           })
       }

Finally we come to Take a look at the management component communication in a single event

html:

<div id="div">
    <com-a></com-a>
    <com-b></com-b>
    <com-c></com-c>
</div>

js code:

<script>
    window.onload = function(){
        const event=new Vue;
        const A={
            template:`
            <div>
                <span>我是A组件---------></span>{{msg1}}
                <input type="button" value="把a组件的数据传给c" @click="send()">
            </div>
            `,
            data(){
                return{
                    msg1:"我是A组件的数据"
                }
            },
            methods:{
                send(){
                    event.$emit("a-data",this.msg1)
                }
            }
        };
        const B={
            template:`
            <div>
                <span>我是B组件---------></span>{{msg2}}
                <input type="button" value="把b组件的数据传给c" @click="send()">
            </div>
            `,
            data(){
                return{
                    msg2:"我是B组件的数据"
                }
            },
            methods:{
                send(){
                    event.$emit("b-data",this.msg2)
                }
            }
        };
        const C={
            template:`
            <div>
                <h3>我是C组件</h3>
                <span>接收到A的数据--->{{a}}</span><br/>
                <span>接收到B的数据--->{{b}}</span>
            </div>
            `,
            data(){
              return{
                  a:"a",
                  b:"b"
              }
            },
            mounted(){
                event.$on("a-data",function (a) {
                    this.a=a;
                }.bind(this));
                event.$on("b-data",function (b) {
                    this.b=b
                }.bind(this))
            }
 
        };
        new Vue({
            el:"#div",
            data:{
                    msg:"我是父组件数据"
            },
            components:{
               "com-a":A,
               "com-b":B,
               "com-c":C
            }
        })
    }
</script>

Related recommendations: "vue.js Tutorial"

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