通过昨天.setDate(currentDay.getDate() - 1) 计算前一天失败

Question

我正在尝试计算当前和前 6 天的日期。这should work 只需从上一个日期减去 1，所以我实现了我当前的解决方案，如下所示：

        let currentDay = new Date();
        let nextDay = new Date();
        for (let i = 0; i < 7; i++) {
            nextDay.setDate(currentDay.getDate() - i);
            console.log("i=" + i + "->" + nextDay);
        }

但是，这是输出：

i = 0 -> Thu Dec 03 2020 10: 20: 51 GMT + 0100(Central European Standard Time)  //today
i = 1 -> Wed Dec 02 2020 10: 20: 51 GMT + 0100(Central European Standard Time)  //yesterday
i = 2 -> Tue Dec 01 2020 10: 20: 51 GMT + 0100(Central European Standard Time)  //day before yesterday
i = 3 -> Mon Nov 30 2020 10: 20: 51 GMT + 0100(Central European Standard Time)  //3 days ago
i = 4 -> Fri Oct 30 2020 10: 20: 51 GMT + 0100(Central European Standard Time)  //skips an entire month
i = 5 -> Mon Sep 28 2020 10: 20: 51 GMT + 0200(Central European Summer Time)    //skips another month, 2 days and switches to summertime
i = 6 -> Fri Aug 28 2020 10: 20: 51 GMT + 0200(Central European Summer Time)    //skips another month

在上个月末运行时，它按预期工作（当前月份没有转义）。它在进入 11 月时失败了。我似乎找不到原因。

Answer 1

您永远不会从第一天开始重新创建nextDate。看看这个：

function addDays(a_oDate: Date, days: number): Date {
  a_oDate.setDate(a_oDate.getDate() + days);
  return a_oDate;
  }

function printLast7Days(a_oDate: Date): void {
  for (let i = 0; i < 7; i++) {
    let nextDay = new Date(a_oDate); // recreate date from the initial date
    addDays(nextDay, -i); // effectively subtracts i days
    console.log("i=" + i + "->" + nextDay.toDateString());
    }
}

printLast7Days(new Date());

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