sortFun1() {
      let arr = ["1", "2", "3", "1", "5"];
      arr = arr.sort((a, b) => {
        return a - b;
      });
      console.log(arr); //排序后['1', '1', '2', '3', '5']
    },
     sortFun2() {
      let arr = [{na:3,ag:"11"},{na:10,ag:"22"},{na:21,ag:"33"},{na:11,ag:"44"},{na:4,ag:"66"}];
      arr = arr.sort((a, b) => {
        return b.na - a.na;
      });
      console.log(arr); //排序后['1', '1', '2', '3', '5']
    },