在某些月份停止增加和减少月份

Question

目前我在一个窗口中显示 6 个月（从 2019 年 11 月到 2019 年 4 月）。用户可以转到上一个/过去 12 个月（直到 2018 年 11 月），并且可以再前进一个月（2019 年 5 月）。用户可以转到前几个月，也可以转到未来几个月，但我需要限制它。

  months: any[] = [];

    date = new Date();   

    month = this.date.getMonth();

    year = this.date.getFullYear()

      ngOnInit() {

          this.getMonths(this.year, this.month);

        }

        getMonths(year:number, month:number) {

        this.months = [];

          for (let i = 0; i < 6; i++) {

            this.months.push(new Date(year, month++));

          }

        }

        getNextData() {

         this.month++;

         this.getMonths(this.year, this.month);

        }

        getPreviousData(){

        this.month--;

       this.getMonths(this.year, this.month);

     }

Answer 1

我认为以下内容可以帮助您。我重写了你的一些函数并引入了一个辅助函数，用于设计以月表示的日期之间的差异。（因此，如果两个日期相隔一年，则此函数将返回 12）。然后，您可以根据它们之间的差异比较两个日期。我还添加了两个值，this.currMonth并且this.currYear使您可以充分比较this.month和this.year它的原始值。这样想，如果要检查 ifthis.month是否大于以前，则无法检查 if，this.month > this.month + 1因为显然this.month不大于自身加一。而且，如果您增加它，您将重新分配该值，并且您将永远无法与this.month比自身大的值进行比较。this.currMonth并且this.currYear是不变的，因此他们总是可以是一个很好的项目进行比较this.year，并this.month当您确定是否要递增/递减。这些函数还决定了年份应该何时改变。例如，如果您返回一个月（从 1 月到 12 月），则需要将年份从 2019 年更新到 2018 年。此外，如果月份为 0（1 月），则不能递减它，因为您将得到 -1，不能用作日期比较的月份。您需要将日期更改为 11。相反，如果您从 12 月递增到 1 月，则需要将this.year2018 年更改为 2019 年，而不是递增this.month（这将给您 13-不是有效月份），您需要将其赋值为 0。months: any[] = [];&nbsp; &nbsp; date = new Date();&nbsp; &nbsp; currMonth = this.date.getMonth();&nbsp; &nbsp; month = this.date.getMonth();&nbsp; &nbsp; currYear = this.date.getFullYear();&nbsp; &nbsp; year = this.date.getFullYear();&nbsp; &nbsp; &nbsp; ngOnInit() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; this.getMonths(this.year, this.month);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; getMonths(year:number, month:number) {&nbsp; &nbsp; &nbsp; &nbsp; this.months = [];&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; for (let i = 0; i < 6; i++) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; this.months.push(new Date(year, month++));&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; getNextData() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;var d1 = new Date(this.currYear, this.currMonth)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;var d2 = new Date(this.year , this.month + 1)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;var diff = this.diff_months(d2, d1)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;if (diff <= 1){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;if (this.month === 11){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;this.month = 0&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;this.year++&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;} else {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;this.month++&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; &nbsp; &nbsp;getPreviousData(){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var m = this.month - 1&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var d1 = new Date(this.currYear, this.currMonth)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (this.month === 0){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var d2 = new Date(this.year-1, 11)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; } else {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var d2 = new Date(this.year, m)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var diff = this.diff_months(d1, d2)&nbsp;&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (diff <= 12){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;if (m < 0){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;this.month = 11&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;this.year--&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;} else {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;this.month--&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp;&nbsp;&nbsp; &nbsp; &nbsp; diff_months = (dt2, dt1) => {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;var diff =(dt2.getTime() - dt1.getTime()) / 1000;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;diff /= (60 * 60 * 24 * 7 * 4);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;return Math.abs(Math.round(diff));&nbsp; &nbsp; &nbsp; }