这种情况是由于你创建Vue对象是缺少new

  var vue = Vue({
            el: "#bj",
            data:{
                title: "无中生有",
                items:["何处","习惯","摸索"]
            }
        });

修改为以下

    var vue = new Vue({
           el: "#bj",
           data:{
               title: "无中生有",
               items:["何处","习惯","摸索"]
           }
       });
   </script>
   ```