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This article brings you knowledge about vue components, including how to instantiate multiple vue objects, global components and local components, as well as passing values from parent to child, etc. I hope it will be helpful to everyone.
Use new creates multiple vue objects and names them, and they can access each other through variables
Example: Object 2 modifies the name variable of object 1
<!-- 第一个根元素 -->
<div>这里是：{{name}}</div>
<!-- 第二个根元素 -->
<div>
<p>这里是：{{name}}</p>
<br>
<button>change-one-name</button>
<!-- 点击后修改vue-app-one的name值-->
</div>
// 第一个vue对象var one = new Vue({
el:"#vue-app-one",
data:{
"name":"ccy1"
}})
// 第二个vue对象var two = new Vue({
el:"#vue-app-two",
data:{
"name":"ccy2"
},
methods:{
// 修改vue-app-one的name为'ccy333'
changeName:function(){
one.name = 'ccy333'
}
}})
Effect: After clicking, modify "ccy1" to "ccy333"
- Define global components, You need to give the component a name. When calling, use the component name as the label name; it is equivalent to a custom label. This label can contain many sub-html tags;
- These sub-html tags are defined in the template attribute of the component , every time the component is called, the tag in the template is rendered
- in the template must have only one root element
- In the component, data is a function, return the data back
- You can still use this to call the data defined in data
Example:
Define component:
① Define a component, named my-component
② It contains data: name and method: changeName
③ The rendered html effect has a p tag, including A button, when the button is clicked, the name is modified
④ Naming convention: camelCase (camel case naming method) and kebab-case (dash separated naming)
- When written as a label, encounter The naming of uppercase letters needs to be changed to lowercase and a cross bar is used to connect the two parts before and after. For example, when defining a component, name it myComponent, and when writing it as a label, it should be written as my-component> ;
- You can also use the horizontal bar method to name components when defining them;
- If you use myComponent when defining and use my-component> for the label, it is OK, the system Automatically identify
// 自定义的全局组件my-component// template中只有一个根元素p标签，里面包含一个button按钮Vue.component('my-component',{
template:`<p>
我的名字是：{{name}}
<button>btn</button>
</p>`,
data(){
return {
name:'ccy'
}
},
methods:{
changeName:function(){
this.name = '安之'
}
}})// vue对象1new Vue({
el:"#vue-app-one",})// vue对象2new Vue({
el:"#vue-app-two",})
Use components:
① Use ## under the root element corresponding to the vue object (el specifies the tag) # ② Since it is a global component, it can be used under any vue object
③ Components are reusable and can be used multiple times under a vue object, and the components are independent of each other<p> <my-component></my-component> <my-component></my-component></p> <p> <my-component></my-component></p>
Effect:
But in the global component, the same data may be used by multiple vue objects. When each object does not maintain a separate copy of data, if a certain vue object is modified If a variable in data is deleted, other vue objects will be affected when they obtain data;
Therefore, in order to ensure the independence of data, that is,In vscode, the data in the component is not allowed to be an object, and an error will be reported:each instance can maintain an independent copy of the returned object, data is Each instance returns a copy of newly created data, and the data obtained by different vue objects does not affect each other
[Vue warn]:
The “data” option should be a function that returns a per-instance value in component definitions.
Local componentsExample:Local components are registered in a vue object.
- Only the vue object that has registered the local component can use this local component
Local component definition:
// template仅一个根元素：ulvar msgComponent = {
// 数据是自身提供的 (hobbies)
template:`
Register local component:
// 仅由注册过该局部组件的vue对象才能使用，此处为p#vue-app-one// 注意命名规范，components中对象的key将会被作为标签名，多个单词拼接的命名需使用横杆法// 可以写成msg-component，此处直接简化了命名为msg，new Vue({
el:"#vue-app-one",
components:{
"msg": msgComponent }})
Use in the html file:
<p> </p><p>这里是vue-app-one</p> <mycomponent></mycomponent> <mycomponent></mycomponent> <p>我的爱好：</p> <msg></msg> <!--使用局部组件-->
Effect: The part circled in the red box is rendered by the local component 
Create subcomponent:
var titleComponent = {
props:["title"],
template:`<p>{{title}}</p>`
// 所需要的数据title由父组件提供}
在父组件的components属性中注册子组件：
new Vue({
el:"#vue-app-one",
components:{
"msg": msgComponent,
"titleComponent":titleComponent },})
在父组件上使用子组件：
<!-- p#vue-app-one为父组件 --><p> </p><p>这里是vue-app-one</p> <mycomponent></mycomponent> <mycomponent></mycomponent> <!--使用子组件title-component，并传值"我的爱好："给子组件--> <title-component></title-component> <msg></msg>
效果：红框标记处就是父向子传值并展示
定义子组件：
var titleComponent = {
props:["title"],
template:`<p>{{title}}</p>`}
在父组件的components属性中注册子组件：
new Vue({
el:"#vue-app-one",
components:{
"msg": msgComponent,
"titleComponent":titleComponent },
data(){
return {
title:"my hobbies are ",
}
}})
使用子组件，通过绑定父组件data中的变量title来实现动态传值：
<!-- p#vue-app-one为父组件 --><p> </p><p>这里是vue-app-one</p> <mycomponent></mycomponent> <mycomponent></mycomponent> <!-- 动态绑定title --> <title-component></title-component> <msg></msg>
效果：红框处就是动态绑定获取数据的展示
传递数组等复杂数据时，也可以使用v-bind来动态传值，如：
需要向子级传递hobbies数组，在vue实例对象（父）中创建数据hobbies：
new Vue({
el:"#vue-app-one",
components:{
"msg": msgComponent,
"titleComponent":titleComponent },
data:{
title:"my hobbies are ",
hobbies:['看剧','看动漫','吃好吃的'], //需要向子组件传递的数据
}})
定义子组件：
var msgComponent = {
template:`
<p>{{hobby}}</p> `,
props:["hobby"],
data(){
return {
}
}}
使用子组件：
<!-- p#vue-app-one为父组件 --><p> </p><p>这里是vue-app-one</p> <mycomponent></mycomponent> <mycomponent></mycomponent> <title-component></title-component> <!-- 动态传值：hobbies --> <msg></msg>
效果：
跳回“一点想法”处
子组件不能通过prop向父组件传递数据，需要使用事件向父组件抛出一个值，告知父组件我需要实现一个功能，由父组件处理这个事件
例子：点击按钮，改变名称chinesename
（由于data变量名不支持chinese-name形式，花括号里不支持chineseName形式，所以这里我都用了小写，此处记录一下，日后学到了新知再来填坑）
先在父组件的data中定义chinesename的初始值：
new Vue({
el:"#vue-app-one",
data:{
chinesename:"anzhi" // chinesename初始值
}})
创建子组件，并注册事件change-name（就像click事件一样，需要让系统能够辨认这是一个事件并监听，当事件被触发时，执行某项约定好的操作）：
Vue.component('blog-post', {
props: ['chinesename'],
template: `
<p>
</p><h3>{{ chinesename }}</h3>
<button>
修改名字
</button>
`
// blog-post组件包含一个h3，显示chinesename，和一个按钮
// 点击这个按钮，触发change-name事件，将"ruosu"作为参数传递给指定的处理函数onChangeName
})
在父组件中使用子组件，定义change-name的处理函数为onChangeName：
<p> </p><p>这里是vue-app-one</p> <!-- v-bind：通过prop给子组件传递chinesename的初始值 --> <!-- v-on：子组件通过$emit给父组件传递新的chinesename的值 --> <p> <blog-post></blog-post> </p>
在父组件处定义事件处理函数onChangeName：
new Vue({
el:"#vue-app-one",
data:{
chinesename:"anzhi"
},
methods:{
onChangeName:function(value){
// 将chinesename换成传递过来的数据
this.chinesename=value }
}})
效果：
关于父子组件的区分，在此写一点总结，还是日后学了新知识再来填坑 ┗|｀O′|┛ 嗷~~
官网中没有很明确指明两者的定义和区别，在网上搜了一圈，觉得比较多人认可并且好理解的是：
在前面这些父子传值的例子中，我们可以看到，对于局部组件，我们会在某个html根元素中注册并使用，所以此时el指定的根元素在html文件中是这个局部组件的父组件，局部组件在html使用时便是这个父组件的一份子，承担数据传输的责任
跳转到父向子动态传值案例
再用绕口令说一波，即：title-component组件定义处与使用处，两者身份是不一样的，在定义处，它是局部组件，也是子组件，需注册才能使用；在使用处，它是根元素的包含一部分，根元素为父组件，而“它”，承担着父组件与子组件数据沟通的重任
这个总结在全局组件情况下也适用，使用该全局组件的根元素是父组件，如上面的子向父传值的案例，p#vue-app-one是父组件，
跳转到子向父案例
图示：
如果是子组件又嵌套了子组件，被嵌套的组件是子子组件，以此类推
You can read my article for CLI scaffolding installation steps. Using CLI scaffolding to create a project is simple and fast. In particular, page content and data transfer need to be written in .vue files, and each vue file is a module.
We complete a specific function by reasonably assembling each module (component). The cooperation between components and the role of parent-child value transfer are more obvious here. Each vue file can be regarded as a component. We can divide the page into several parts according to needs, such as navigation bar, middle content and bottom part. The implementation of each part is dispersed into various sub-components, including page display and data acquisition.
## The schematic diagram of personal blog passing value from parent to child is as follows:For example, a customized blog page:
The main page is composed of the vue-app main component, including the navigation bar, the middle part, and the bottom bar
The navigation bar is completed by the vue-header sub-component
The middle content is divided according to functions
- Add blog: addBlob sub-component Component
- Display blog: showBlob subcomponent
- Modify blog: modifyBlob subcomponent
- Click to display single blog content: singleBlob subcomponent
The bottom information bar is completed by vue-footer
In addition to the main page, other sub-parts and components are divided according to functions to assist the main page display
vue.js tutorial"】
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