testing date-related functions

date.spec.ts

/**
 * @jest-environment jsdom
 * @jest-environment-options {"url": "https://website.com"}
 */

import { defaultPeriod } from "../../src/utils/date";

let windowSpy: ReturnType<typeof jest.spyOn>;

describe("test date.ts", () => {
  describe("defaultPeriod()", () => {
    beforeEach(() => {
      windowSpy = jest.spyOn(window, "window", "get");
    });

    afterEach(() => {
      windowSpy.mockRestore();
    });

    test("sets start to yesterday & end to currentMonthStart", () => {
      const date = "2021-01-10";
      const start = "2021-01-01";
      const end = "2021-01-09";

      const search = window.location.search;

      jest
        .useFakeTimers()
        .setSystemTime(new Date(date));

      if (!search) {
        expect(defaultPeriod()).toMatchObject({ start, end });
      }
    });

    test("sets the search params", () => {
      const start = "2021-01-01";
      const end = "2021-01-10";

      windowSpy.mockImplementation(() => ({
        location: {
          search: `?start=${start}&end=${end}`,
        },
      }));

      expect(defaultPeriod()).toMatchObject({ start, end });
    });

    test("sets the whole previous month if today is the first day of the month", () => {
      const date = "2021-02-01";
      const start = "2021-01-01";
      const end = "2021-01-31";

      jest
        .useFakeTimers()
        .setSystemTime(new Date(date));

      expect(defaultPeriod()).toMatchObject({ start, end });
    });

    test("sets the first day of the month if today is the second day of the month", () => {
      const date = "2021-01-02";
      const currentMonthStart = "2021-01-01";

      jest
        .useFakeTimers()
        .setSystemTime(new Date(date));

      expect(defaultPeriod()).toMatchObject({ start: currentMonthStart, end: currentMonthStart });
    });
  });
});

date.ts

import dayjs from "dayjs";

export function formatDate(date: Date | string, format = "ddd, D MMM YYYY, HH:mm Z"): string {
  return dayjs(date).format(format);
}

export function representDate(date: Date | string, size: "month" | "day" | "hour" = "hour", includeTimezone = true): string {
  switch (size) {
    case "month":
      return dayjs(date).format("MMM YYYY");
    case "day":
      return dayjs(date).format("ddd, D MMM YYYY");
    case "hour":
      return dayjs(date).format(`ddd, D MMM YYYY, HH:mm ${includeTimezone && "Z"}`);
    default:
      return dayjs(date).format(`ddd, D MMM YYYY, HH:mm ${includeTimezone && "Z"}`);
  }
}

export function defaultPeriod() {
  let period: { start: string, end: string };

  const dateFormat = "YYYY-MM-DD";
  const queryObject: Record<string, string> = {};
  const queryParams = window.location.search
    .slice(1) // remove "?" from the query string
    .split("&");

  queryParams.forEach(param => {
    queryObject[param.split("=")[0]] = param.split("=")[1];
  });

  const today = dayjs().format(dateFormat);
  const yesterday = dayjs().subtract(1, "day").format(dateFormat);
  const currentMonthStart = dayjs().format("YYYY-MM-[01]");

  // ? Today is the first day of the current month
  if (dayjs(today).valueOf() === dayjs(currentMonthStart).valueOf()) {
    const prevMonthStart = dayjs(currentMonthStart).subtract(1, "month").format(dateFormat);
    const prevMonthEnd = dayjs(currentMonthStart).subtract(1, "day").format(dateFormat);

    period = {
      start: prevMonthStart,
      end: prevMonthEnd,
    };

    // ? Yesterday was the first day of the current month
  } else if (dayjs(yesterday).valueOf() === dayjs(currentMonthStart).valueOf()) {
    period = {
      start: currentMonthStart,
      end: currentMonthStart,
    };
  } else {
    period = {
      start: currentMonthStart,
      end: yesterday,
    };
  }

  if (
    queryObject.start &&
    queryObject.end &&
    new Date(queryObject.start).getTime() <= new Date(queryObject.end).getTime() &&
    dayjs(queryObject.start, dateFormat, true).isValid() &&
    dayjs(queryObject.end, dateFormat, true).isValid()
  ) {
    period = {
      start: queryObject.start,
      end: queryObject.end,
    };
  }

  return period;
}