[Vue] 14.Vue中的组件：创建子组件以及在父组件中用子组件

一、父组件

创建父组件的实例如下：

<script>
        const app = Vue.createApp({
            template: `<div>hello world</div>`
        });
        const vm = app.mount('#root')
    </script>

定义两个全局子组件‘hello’和’world’

<script>
        const app = Vue.createApp({
            template: `<div>hello world</div>`
        });
        app.component('hello', {
            template: `<div>hello</div>`
        })
        app.component('world', {
            template: `<div>world</div>`
        })
        const vm = app.mount('#root')
    </script>

调用子组件：直接用子组件标签就可调用

<script>
        const app = Vue.createApp({
            template: `<div><hello/><world/></div>`
        });
        app.component('hello', {
            template: `<div>hello</div>`
        })
        app.component('world', {
            template: `<div>world</div>`
        })
        const vm = app.mount('#root')
    </script>

在这里插入图片描述
注：通过app.component定义的组件是全局组件，在哪里都可以使用，但是这种全局创建的组件对性能会有影响

定义局部组件：注册后才能使用，性能比较高，使用起来比较麻烦

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>14</title>
    <script src="https://unpkg.com/vue@next"></script>
</head>
<body>
    <div id="root"></div>
    <script>
        const Counter = {
            data() {
                return {
                    count: 1
                }
            },
            template: `<div @click="count += 1">{{count}}</div>`
        }
        const app = Vue.createApp({
            components: {counter: Counter},
            template: `<div><counter/></div>`
        });
        const vm = app.mount('#root')
    </script> 
</body>
</html>

自定义子组件的标签

<script>
        const Counter = {
            data() {
                return {
                    count: 1
                }
            },
            template: `<div @click="count += 1">{{count}}</div>`
        }
        const app = Vue.createApp({
            components: {'dell': Counter},
            template: `<div><dell /></div>`
        });
        const vm = app.mount('#root')
    </script>