eOMonth_test.js

eOMonth_test.js

const eOMonth = (date) => (new Date(date.getFullYear(),date.getMonth()+1,0))
const formattedDate = (date) => (date.getFullYear() + '-' + String(date.getMonth() + 1).padStart(2, '0') + '-' + String(date.getDate()).padStart(2, '0'))

/// test today, prev month
const today = new Date()
const prevMonthStartDate = new Date(today.getFullYear(),today.getMonth()-1,1)
const prevMonthEndDate = new Date(today.getFullYear(),today.getMonth(),0)

console.log(formattedDate(today))
console.log(formattedDate(prevMonthStartDate))
console.log(formattedDate(prevMonthEndDate))

console.log(formattedDate(eOMonth(today)))
console.log(formattedDate(eOMonth(prevMonthStartDate)))
console.log(formattedDate(eOMonth(prevMonthEndDate)))

console.log(formattedDate(eOMonth(eOMonth(today))))

/// test new year and before
const newYear = new Date(2021, 0, 1) // january is 0
const beforeNewYear = new Date(newYear.getFullYear(),newYear.getMonth(),0)

console.log(formattedDate(newYear))
console.log(formattedDate(beforeNewYear))
console.log(formattedDate(eOMonth(newYear)))
console.log(formattedDate(eOMonth(beforeNewYear)))