小程序setData中key用变量

Page({
  data:{
    //类型列表
    lastRootList:0,//上次点击的类型
    rootList:[{name:'服饰箱包',selectClass:'root-active',iconClass:'bag'},
              {name:'家居生活',selectClass:'',iconClass:'furniture'},
              {name:'母婴玩具',selectClass:'',iconClass:'baby'},
              {name:'食品饮料',selectClass:'',iconClass:'food'},
              {name:'数码电器',selectClass:'',iconClass:'appliances'}]
  },
rootItem_bindtap:function(e){
var key='rootList';
    nav="更新的数据";
    //更新nav数据
    this.setData({
      [key]:nav
    });
  }
})