为什么Date（）返回错误的日期？

Question

我有以下功能：

public static addDaysNextPrev(operation: number, date: Date = new Date(), days: number = 7): IDateCalendarNextPrev {
    const currentDate = new Date(date);
    const prevDate = new Date(date);

    currentDate.setDate(currentDate.getDate() + (days * operation));
    prevDate.setDate(currentDate.getDate() - (days * operation));
    console.log(prevDate);

}

我尝试添加/减去当前日期的某些天。想法是将7天添加到当前日期并返回上一个和下一个。

参数operation是数字1或正数或负数，用于确定下一个日期或上一个日期的方向。

我总是排错日期：

console.log(prevDate);

这是我的第二个解决方案，更明显：

public static addDaysNextPrev(operation: boolean, date: Date = new Date(), days: number = 7): IDateCalendarNextPrev {
    let currentDate = new Date(date);
    let prevDate = new Date(date);

    if (operation) {
      prevDate = date;
      currentDate.setDate(currentDate.getDate() + days);
    } else {
      currentDate.setDate(date.getDate() - days);
      prevDate.setDate(currentDate.getDate() - days);
    }
}

Answer 1

您在第currentDate行添加了7天的时间：

currentDate.setDate(currentDate.getDate() + (days * operation));

并在该行减去currentDate的7天：

prevDate.setDate(currentDate.getDate() - (days * operation));

因此，您的prevDate将与currentDate初始值具有相同的值。

此处更正：

let operation = 1;
let date: Date = new Date();
let days: number = 7

const currentDate = new Date(date);
const prevDate = new Date(date);

prevDate.setDate(currentDate.getDate() - (days * operation));

console.log(prevDate);