How to handle edge cases for checking whether the given date is last month or not?

Question

I have a function as follows it takes in a date and checks whether the given date is in last month or not.

const { 
subMonths, 
getMonth, 
lastDayOfMonth, 
startOfMonth, 
isWithinInterval 
} = require('date-fns')

function isLastMonth(date) {

    let lastMonthDateOfGivenDate = subMonths(new Date(date), 1)

    let today = Date.now()
    let lastMonthDate = subMonths(today, 1);

    let firstDayOfLastMonth = startOfMonth(lastMonthDate)
    let lastDayOfLastMonth = lastDayOfMonth(lastMonthDate)

    if (isWithinInterval(lastMonthDateOfGivenDate, { start: firstDayOfLastMonth, end: lastDayOfLastMonth }))
        console.log("true")
    else
        console.log('false')

}

isLastMonth("2020-03-30T15:24:02.647Z")

The problem is is I'm not able to check for dates which have 31 days or 30 days for february.

Any solution or other approach for this problem? Thank you.

Maybe this can help, if you didn't saw this answers already: [how-to-validate-date-if-is-the-last-day-of-the-month-with-javascript](https://stackoverflow.com/questions/6355063/how-to-validate-date-if-is-the-last-day-of-the-month-with-javascript) — Mara Black, Mar 30 '20 at 06:59

score 1 · Answer 1 · answered Mar 30 '20 at 07:40

The solution is as follows

import {subMonths, startOfMonth, endOfMonth, isWithinInterval} from 'date-fns'

function isLastMonth(date) {

    let today = Date.now()
    let lastMonthDate = subMonths(today, 1);

    let firstDayOfLastMonth = startOfMonth(lastMonthDate)
    let lastDayOfLastMonth = endOfMonth(lastMonthDate)

    return isWithinInterval(new Date(date), { start: firstDayOfLastMonth, end: lastDayOfLastMonth })

}

All the edge cases will be handled by javascript itself; for example, the previous month date of May 31, 2020, will be April 30 2020.

How to handle edge cases for checking whether the given date is last month or not?

1 Answers1