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vue 组件基础知识总结

时间：2021-03-28 09:15:45 | 栏目：vue | 点击：次

组件基础

1 组件的复用

组件是可复用的Vue实例。

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">  
  <style>
   
  </style>
  <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
 </head>
 <body>
		<div id="app">
			<button-counter></button-counter>
			<button-counter></button-counter>
			<button-counter></button-counter>
		</div>
  <script>
			// 定义一个名为 button-counter 的新组件
			Vue.component('button-counter', {
				data: function () {
					return {
						count: 0
					}
				},
				template: '<button v-on:click="count++">点击了 {{ count }} 次.</button>'
			});

			new Vue({ el: '#app' });
  </script>
 </body>
</html>

注意当点击按钮时，每个组件都会各自独立维护它的count。这里自定义组件的data属性必须是一个函数，每个实例维护一份被返回对象的独立的拷贝。

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">  
  <style>
   
  </style>
  <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
 </head>
 <body>
		<div id="app">
			<button-counter></button-counter>
			<button-counter></button-counter>
			<button-counter></button-counter>
		</div>
  <script>
			var buttonCounterData = {
				count: 0
			}
			// 定义一个名为 button-counter 的新组件
			Vue.component('button-counter', {
				data: function () {
					return buttonCounterData
				},
				template: '<button v-on:click="count++">点击了 {{ count }} 次.</button>'
			});

			new Vue({ el: '#app' });
  </script>
 </body>
</html>

2 通过 Prop 向子组件传递数据

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">  
  <style>
   
  </style>
  <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
 </head>
 <body>
		<div id="app">
			<blog-post title="My journey with Vue"></blog-post>
			<blog-post title="Blogging with Vue"></blog-post>
			<blog-post title="Why Vue is so fun"></blog-post>
		</div>
  <script>
			Vue.component('blog-post', {
				props: ['title'],
				template: '<h3>{{ title }}</h3>'
			})

			new Vue({ el: '#app' });
  </script>
 </body>
</html>

这里<blog-post>组件就是通过自定义属性title来传递数据。
我们可以使用v-bind来动态传递prop。

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">  
  <style>
   
  </style>
  <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
 </head>
 <body>
		<div id="app">
			<blog-post v-for="post in posts" v-bind:key="post.id" v-bind:title="post.title"></blog-post>
		</div>
  <script>
			Vue.component('blog-post', {
				props: ['title'],
				template: '<h3>{{ title }}</h3>'
			})

			new Vue({
				el: '#app',
				data: {
					posts: [
						{ id: 1, title: 'My journey with Vue' },
						{ id: 2, title: 'Blogging with Vue' },
						{ id: 3, title: 'Why Vue is so fun' }
					]
				}
			});
  </script>
 </body>
</html>

3 单个根元素

每个组件必须只有一个根元素。

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">  
  <style>
   
  </style>
  <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
 </head>
 <body>
		<div id="app">
			<blog-post v-for="post in posts" v-bind:key="post.id" v-bind:post="post"></blog-post>
		</div>
  <script>
			Vue.component('blog-post', {
				props: ['post'],
				template: `
					<div class="blog-post">
						<h3>{{ post.title }}</h3>
						<div v-html="post.content"></div>
					</div>
				`
			})

			new Vue({
				el: '#app',
				data: {
					posts: [
						{ id: 1, title: 'My journey with Vue', content: 'my journey...' },
						{ id: 2, title: 'Blogging with Vue', content: 'my blog...' },
						{ id: 3, title: 'Why Vue is so fun', content: 'Vue is so fun...' }
					]
				}
			});
  </script>
 </body>
</html>

注意到v-bind:post="post"绑定的post是一个对象，这样可以避免了需要通过很多prop传递数据的麻烦。

4 监听子组件事件

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">  
  <style>
   
  </style>
  <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
 </head>
 <body>
		<div id="app">
			<div :style="{fontSize: postFontSize + 'em'}">
				<blog-post v-for="post in posts" 
					v-bind:key="post.id" 
					v-bind:post="post"
					v-on:enlarge-text="postFontSize += 0.1" />
			</div>			
		</div>
  <script>
			Vue.component('blog-post', {
				props: ['post'],
				template: `
					<div class="blog-post">
						<h3>{{ post.title }}</h3>
						<button v-on:click="$emit('enlarge-text')">放大字体</button>
						<div v-html="post.content"></div>
					</div>
				`
			})

			new Vue({
				el: '#app',
				data: {
					postFontSize: 1,
					posts: [
						{ id: 1, title: 'My journey with Vue', content: 'my journey...' },
						{ id: 2, title: 'Blogging with Vue', content: 'my blog...' },
						{ id: 3, title: 'Why Vue is so fun', content: 'Vue is so fun...' }
					]
				}
			});
  </script>
 </body>
</html>

子组件通过$emit方法并传入事件名称来触发一个事件。父组件可以接收该事件。

我们可以使用事件抛出一个值。

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">  
  <style>
   
  </style>
  <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
 </head>
 <body>
		<div id="app">
			<div :style="{fontSize: postFontSize + 'em'}">
				<blog-post v-for="post in posts" 
					v-bind:key="post.id" 
					v-bind:post="post"
					v-on:enlarge-text="postFontSize += $event" />
			</div>			
		</div>
  <script>
			Vue.component('blog-post', {
				props: ['post'],
				template: `
					<div class="blog-post">
						<h3>{{ post.title }}</h3>
						<button v-on:click="$emit('enlarge-text', 0.2)">放大字体</button>
						<div v-html="post.content"></div>
					</div>
				`
			})

			new Vue({
				el: '#app',
				data: {
					postFontSize: 1,
					posts: [
						{ id: 1, title: 'My journey with Vue', content: 'my journey...' },
						{ id: 2, title: 'Blogging with Vue', content: 'my blog...' },
						{ id: 3, title: 'Why Vue is so fun', content: 'Vue is so fun...' }
					]
				}
			});
  </script>
 </body>
</html>

在父组件中，我们可以通过$event访问到被抛出的这个值。
我们可以在组件上使用v-model。

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">  
  <style>
   
  </style>
  <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
 </head>
 <body>
		<div id="app">
			<!-- <input v-model="searchText"> -->
			<input v-bind:value="searchText" v-on:input="searchText = $event.target.value">
			<p>{{ searchText }}</p>
		</div>
  <script>
			new Vue({
				el: '#app',
				data: {
					searchText: ''
				}
			});
  </script>
 </body>
</html>
<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">  
  <style>
   
  </style>
  <script src="https://cdn.staticfile.org/vue/2.4.2/vue.min.js"></script>
 </head>
 <body>
		<div id="app">
			<custom-input v-model="searchText"></custom-input>
			<custom-input v-bind:value="searchText" v-on:input="searchText = $event"></custom-input>
			<p>{{ searchText }}</p>
		</div>
  <script>
			Vue.component('custom-input', {
				props: ['value'],
				template: `<input v-bind:value="value" v-on:input="$emit('input', $event.target.value)" >`
			})

			new Vue({
				el: '#app',
				data: {
					searchText: ''
				}
			});
  </script>
 </body>
</html>

最后，注意解析 DOM 模板时的注意事项。

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