js日期、天数计算方式

getBeforeDate(n) {

    let myDate = new Date();

    myDate.setDate(myDate.getDate() - (n - 1));

    let dateArray = [];

    let dateTemp;

    let flag = 1;

    for (let i = 0; i < n; i++) {

      dateTemp = myDate.getFullYear() + "-" +(myDate.getMonth() + 1) + "-" + myDate.getDate();

      dateArray.push(dateTemp);

      myDate.setDate(myDate.getDate() + flag);

    }

    return dateArray

  }

例子：前七天   this.getBeforeDate(7)

           前一个月 this.getBeforeDate(30)