利用vue-router实现二级菜单内容转换

<div id="app">
 <div class="leftBox">
 <!-- 使用 router-link 组件来导航. -->
 <!-- 通过传入 `to` 属性指定链接. -->
 <!-- <router-link> 默认会被渲染成一个 `<a>` 标签 -->
 <ul>
 <li><router-link to="/" actived>首页</router-link></li>
 <li><router-link to="/article">文章</router-link></li>
 <li><router-link to="/picture">图片</router-link></li>
 <li><router-link to="/music">音乐</router-link></li>
 </ul>
 </div>
 <div class="rightBox">
 <!-- 路由出口 -->
 <!-- 路由匹配到的组件将渲染在这里 -->
 <router-view></router-view>
 </div>
</div>

var Home = {template: '<div>home</div>'}

var router = new VueRouter({
 routes: [
 {path: '/', component: Home},
 {path: '/picture', component: Picture},
 {path: '/music', component: Music},
 {path: '/article', component: Artlist},
 {path: '/article/:id', component: Article}
 ]
})
new Vue({
 el: "#app",
 router: router
})

var Article = {
 template: '<div class="post">\
 <div class="loading" v-if="loading">loading.....</div>\
 <transition name="slide">\
 <div v-if="post" class="content" :key="post.id">\
 <button @click="back">返回</button>\
 <p>{{post.title}}</p>\
 <P>{{post.body}}</P>\
 </div>\
 </transition>\
 </div>',
 data: function() {
 return {
 loading: false,
 error: null,
 post: null
 }
 },
 created:function() {
 this.fetchData();
 },
 watch: {
 '$route': 'fetchData'
 },
 methods: {
 fetchData:function () {
 this.error = this.post = null;
 this.loading = true;
 getPost(this.$route.params.id,(err,post) => {
 this.loading = false;
 if(err) {
 this.error = err.toString();
 }else {
 this.post = post
 }
 })
 },
 back: function() {
 router.go(-1);
 }
 }
}