如何显示年份的最后一个月？

Question

I have stored the date Nov. 1, 2020 in the variable fiscalYearStart and would like to output Oct. 2020 . Can you please show me how to do this? I have written a function, but I get the message ERROR TypeError: fiscalYearStart.getMonth is not a function

My function:

public getLastMonth () {
    this.navService.getBeginningOfFiscalYear().subscribe((yearResp: any) => {
      if (yearResp && yearResp.success) {
        const fiscalYearStart = yearResp.fiscalYearStart;
        fiscalYearStart.setMonth(fiscalYearStart.getMonth() - 1);
        const lastMonth = new Date(fiscalYearStart);
        console.log(lastMonth);
      }
    });
  }

Answer 1

您应该使用Date构造函数，因为fiscalYearStart它是一个字符串并且没有getMonth方法。

const fiscalYearStart = new Date(yearResp.fiscalYearStart);

Answer 2

public getLastMonth () {
    this.navService.getBeginningOfFiscalYear().subscribe((yearResp: any) => {
      if (yearResp && yearResp.success) {
        const fiscalYearStart = new Date(yearResp.fiscalYearStart);
        fiscalYearStart.setMonth(fiscalYearStart.getMonth() - 1);
        const lastMonth = new Date(fiscalYearStart);
        console.log(lastMonth);
      }
    });
  }