methods中定義了一個匿名函數，訪問data中數據時顯示undefined代碼如下：        var vm = new Vue({            el:"#root",            data:{                show:true             },            methods:{                handleclick:function() {                    console.log(this.show);                    var timer = function() {                        console.log(this.show);                     }                     timer();                 }             }         })控制臺截圖：