vue 組件基礎知識總結
組件是可復用的Vue實例。
<!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>// 定義一個名為 button-counter 的新組件Vue.component(’button-counter’, {data: function () {return {count: 0}},template: ’<button v-on:click='count++'>點擊了 {{ count }} 次.</button>’});new Vue({ el: ’#app’ }); </script> </body></html>
注意當點擊按鈕時，每個組件都會各自獨立維護它的count。這里自定義組件的data屬性必須是一個函數，每個實例維護一份被返回對象的獨立的拷貝。
<!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}// 定義一個名為 button-counter 的新組件Vue.component(’button-counter’, {data: function () {return buttonCounterData},template: ’<button v-on:click='count++'>點擊了 {{ count }} 次.</button>’});new Vue({ el: ’#app’ }); </script> </body></html>2 通過 Prop 向子組件傳遞數據
<!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></blog-post><blog-post></blog-post><blog-post></blog-post></div> <script>Vue.component(’blog-post’, {props: [’title’],template: ’<h3>{{ title }}</h3>’})new Vue({ el: ’#app’ }); </script> </body></html>
這里<blog-post>組件就是通過自定義屬性title來傳遞數據。我們可以使用v-bind來動態傳遞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 單個根元素
每個組件必須只有一個根元素。
<!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'綁定的post是一個對象，這樣可以避免了需要通過很多prop傳遞數據的麻煩。
4 監聽子組件事件<!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='$emit(’enlarge-text’)'>放大字體</button><div v-html='post.content'></div></div>`})new Vue({el: ’#app’,data: {postFontSize: 1,posts: [{ id: 1, title: ’My journey with Vue’, content: ’my journey...’ },{ id: 2, title: ’Blogging with Vue’, content: ’my blog...’ },{ id: 3, title: ’Why Vue is so fun’, content: ’Vue is so fun...’ }]}}); </script> </body></html>
子組件通過$emit方法并傳入事件名稱來觸發一個事件。父組件可以接收該事件。
我們可以使用事件拋出一個值。
<!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)'>放大字體</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>
在父組件中，我們可以通過$event訪問到被拋出的這個值。我們可以在組件上使用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 模板時的注意事項。
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