vue小白请教我在路由里面添加了个占位符为什么点击了add不显示3333数据了

<!DOCTYPE html>


    
    
    
    Document
    
    


    

       {{title}}
       开始
       结束
       添加
       列表
       
    

    
        

                
  • 11111

    •         

    
    
            

                    
  • 2222

    •             

        
    
        

                
  • 3333

    •         

    
     <p>        const index = {template:&#39;#index&#39;}<br>         const back = {template:&#39;#back&#39;}<br>         const add = {template:&#39;#add&#39;}<br>         const routes = [<br>             {<br>                 path:&#39;/index&#39;,<br>                 component:index<br>             },<br>             {<br>                 path:&#39;/back&#39;,<br>                 component:back<br>             },<br>             {<br>                 path:&#39;/add:id&#39;,<br>                 component:add<br>             }<br>         ];</p> <p>        const router = new VueRouter({<br>             routes<br>         })<br>        new Vue({<br>            el:&#39;#app&#39;,<br>            router,<br>            data:{<br>                title:&#39;你好&#39;<br>            },</p> <p>           components:{<br>                index,<br>                back,<br>                add<br>            }</p> <p>       })<br>