datemapper/src/date-between.ts

A lightweight date utility for format conversion, validation, and date manipulation.

import * as moment from "moment-timezone";
import validateDate from "./validate-date";
import { TIncrementType } from "./types";

/**
 * Increments a date by a specified amount based on the increment type.
 * Ensures timezone adjustments are correctly applied.
 *
 * @param date - The starting date to be incremented.
 * @param incrementType - The type of increment to apply ('day', 'month', 'hour', 'year', 'week').
 * @param timezone - The timezone to use for the new date.
 * @returns A new Date object incremented according to the specified type.
 * @throws Will throw an error if an invalid increment type is provided.
 */
const incrementDate = (date: Date, incrementType: TIncrementType, timezone: string): Date => {
  const momentDate = moment.tz(date, timezone); // Apply timezone

  switch (incrementType) {
    case "day":
      return momentDate.add(1, "day").startOf("day").toDate();
    case "month":
      return momentDate.add(1, "month").startOf("month").toDate();
    case "hour":
      return momentDate.add(1, "hour").startOf("hour").toDate();
    case "year":
      return momentDate.add(1, "year").startOf("year").toDate();
    case "week":
      return momentDate.add(1, "week").startOf("week").toDate(); // Add 7 days for a week
    default:
      throw new Error("Invalid increment type");
  }
};

/**
 * Generates an array of dates between two specified dates, incremented by a given type and formatted.
 * Ensures all dates are correctly adjusted for the specified timezone.
 *
 * @param from - The start date in string format (YYYY-MM-DD).
 * @param to - The end date in string format (YYYY-MM-DD).
 * @param ic - The type of increment to apply between the start and end dates.
 * @param timezone - The timezone in which the dates should be interpreted (default: "UTC").
 * @param out - The moment.js format string to be applied to each date in the output array. Defaults to 'YYYY-MM-DD'.
 * @returns An array of strings representing dates between the start and end dates, formatted according to `out`.
 */
const datesBetween = (
  from: string,
  to: string,
  ic: TIncrementType,
  out = "YYYY-MM-DD",
  timezone = "UTC"
): string[] => {
  const { from: fromDate, to: toDate } = validateDate({ from, to }, timezone);
  const array: string[] = [];

  // Convert fromDate to moment object with timezone
  let currentDate = moment.tz(fromDate, timezone);

  // Loop until we reach the end date
  while (currentDate.isSameOrBefore(moment.tz(toDate, timezone))) {
    array.push(currentDate.format(out));
    currentDate = moment.tz(incrementDate(currentDate.toDate(), ic, timezone), timezone);
  }

  return array;
};

export default datesBetween;