Função Typescript para gerar um intervalo de objetos Date Javascript para ser utilizado na construção de calendários de meses

getMonthBehavior.ts

const makeDate = (year: number, month: number, day: number) =>
  new Date(year, month, day, 0, 0, 0)

const makeRangeBetweenDates = (start: Date, end: Date) => {
  const range: Date[] = []

  for (
    const i = new Date(start);
    i.getTime() <= end.getTime();
    i.setDate(i.getDate() + 1)
  ) {
    range.push(new Date(i))
  }

  return range
}

export function getMonthBehavior(date?: Date) {
  const currentDate = date || new Date()

  const firstDate = makeDate(
    currentDate.getFullYear(),
    currentDate.getMonth(),
    1,
  )

  const lastDate = makeDate(
    currentDate.getFullYear(),
    currentDate.getMonth() + 1,
    0,
  )

  const firstDateInRange = makeDate(
    firstDate.getFullYear(),
    firstDate.getMonth(),
    -firstDate.getDay() + 1,
  )

  const lastDateInRange = makeDate(
    lastDate.getFullYear(),
    lastDate.getMonth(),
    lastDate.getDate() + (7 - lastDate.getDay() - 1),
  )

  const range = makeRangeBetweenDates(firstDateInRange, lastDateInRange)

  return {
    currentDate,
    firstDate,
    firstDateInRange,
    lastDate,
    lastDateInRange,
    range,
  }
}