js日期格式化函数Data

Date.prototype.format = function(fmt) {
    var o = {
      "M+": this.getMonth() + 1, //月份
      "d+": this.getDate(), //日
      "h+": this.getHours(), //小时
      "m+": this.getMinutes(), //分
      "s+": this.getSeconds(), //秒
      "q+": Math.floor((this.getMonth() + 3) / 3), //季度
      S: this.getMilliseconds() //毫秒
    };
    if (/(y+)/.test(fmt)) {
      fmt = fmt.replace(
        RegExp.$1,
        (this.getFullYear() + "").substr(4 - RegExp.$1.length)
      );
    }
    for (var k in o) {
      if (new RegExp("(" + k + ")").test(fmt)) {
        fmt = fmt.replace(
          RegExp.$1,
          RegExp.$1.length == 1
            ? o[k]
            : ("00" + o[k]).substr(("" + o[k]).length)
        );
      }
    }
    return fmt;
  };

  mounted() {
    let that = this;
    let date = new Date();
    date.setDate(date.getDate() - 1);
    that.timeDefaultShow = date.format("yyyy-MM-dd");
    that.mounthDefaultShow = date.getFullYear() + "-" + date.getMonth();
    that.sendHomeData();
  }