🕤 dateDiff() - returns a detail object about the difference between two dates

dateDiff.spec.ts

describe('date-diff', () => {
  it('Should check if no date diff results shown for comparing exact same dates', () => {
    const date0 = new Date('2020-11-01T01:00:00');
    const date1 = new Date('2020-11-01T01:00:00');
    const expectedResult = {
      millennium: 0,
      century: 0,
      decade: 0,
      year: 0,
      quarter: 0,
      month: 0,
      week: 0,
      day: 0,
      hour: 0,
      minute: 0,
      second: 0,
      millisecond: 0,
    };
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(expectedResult);
  });

  it('Should check if date diff results contains 1 millennium for comparing dates', () => {
    const date0 = new Date('1017-11-21T04:04:05');
    const date1 = new Date('2022-07-01T00:50:11');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(
      jasmine.objectContaining({
        millennium: 1,
        year: 5,
        quarter: 1,
        week: 1,
        day: 3,
      })
    );
  });

  it('Should check if date diff results contains 1 century for comparing dates', () => {
    const date0 = new Date('1910-01-01T04:04:05');
    const date1 = new Date('2022-09-01T06:50:10');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(
      jasmine.objectContaining({
        century: 1,
        decade: 1,
        year: 2,
        quarter: 3,
        day: 1,
      })
    );
  });

  it('Should check if date diff results contains 2 decades for comparing dates', () => {
    const date0 = new Date('2001-01-01T00:00:05');
    const date1 = new Date('2022-08-01T01:00:10');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(
      jasmine.objectContaining({
        decade: 2,
        year: 1,
        quarter: 2,
        month: 1,
        week: 1,
        day: 0,
        hour: 1,
      })
    );
  });

  it('Should check if date diff results contains 5 years for comparing dates', () => {
    const date0 = new Date('2017-05-01T00:00:00');
    const date1 = new Date('2022-08-03T01:06:00');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(
      jasmine.objectContaining({
        year: 5,
        quarter: 1,
        day: 5,
        hour: 1,
        minute: 6,
      })
    );
  });

  it('Should check if date diff results contains 1 quarter for comparing dates', () => {
    const date0 = new Date('2022-05-01T00:00:00');
    const date1 = new Date('2022-08-08T00:00:00');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(
      jasmine.objectContaining({
        quarter: 1,
        week: 1,
        day: 2,
      })
    );
  });

  it('Should check if date diff results contains 2 months for comparing dates', () => {
    const date0 = new Date('2022-05-01T00:00:00');
    const date1 = new Date('2022-07-03T00:00:00');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(jasmine.objectContaining({ month: 2 }));
  });

  it('Should check if date diff results contains 3 weeks and one day for comparing dates', () => {
    const date0 = new Date('2022-07-31T00:06:00');
    const date1 = new Date('2022-08-22T00:07:00');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(jasmine.objectContaining({ week: 3, day: 1 }));
  });

  it('Should check if date diff results contains 4 days for comparing dates', () => {
    const date0 = new Date('1990-02-10T00:24:00');
    const date1 = new Date('1990-02-14T01:24:00');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(jasmine.objectContaining({ day: 4 }));
  });

  it('Should check if date diff results contains 2 hours for comparing dates', () => {
    const date0 = new Date('1990-11-10T03:24:00');
    const date1 = new Date('1990-11-10T05:24:00');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(jasmine.objectContaining({ hour: 2 }));
  });

  it('Should check if date diff results contains 30 minutes for comparing dates', () => {
    const date0 = new Date('1995-12-17T03:24:00');
    const date1 = new Date('1995-12-17T03:54:00');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(jasmine.objectContaining({ minute: 30 }));
  });

  it('Should check if date diff results contains 45 seconds for comparing dates', () => {
    const date0 = new Date('2000-12-17T03:00:00');
    const date1 = new Date('2000-12-17T03:00:45');
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(jasmine.objectContaining({ second: 45 }));
  });

  it('Should check if date diff results contains 1 millisecond for comparing dates, when initial date is before final date', () => {
    const date0 = new Date(1661817326554);
    const date1 = new Date(1661817326555);
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(jasmine.objectContaining({ millisecond: 1 }));
  });

  it('Should check if date diff results contains 1 millisecond for comparing dates, when initial date is after final date', () => {
    const date0 = new Date(1661817326555);
    const date1 = new Date(1661817326554);
    const dateDiffResult = dateDiff(date0, date1);
    expect(dateDiffResult).toEqual(jasmine.objectContaining({ millisecond: 1 }));
  });
});

dateDiff.ts

const DATE_DIFF_DEF = Object.freeze({
  millennium: 31536000000000,
  century: 3153600000000,
  decade: 315360000000,
  year: 31536000000,
  quarter: 7776000000,
  month: 2592000000,
  week: 604800000,
  day: 86400000,
  hour: 3600000,
  minute: 60000,
  second: 1000,
  millisecond: 1,
});

export type DateDiffKey = keyof typeof DATE_DIFF_DEF;
export type DateDifference = Record<DateDiffKey, number>;

const DATE_DIFF_KEYS = Object.freeze(Object.keys(DATE_DIFF_DEF)) as DateDiffKey[];

/**
 * ☃ dateDiff "Snowman Carl" (http://stackoverflow.com/questions/13903897)
 * Returns a detail object about the difference between two dates
 *
 * When providing custom units, provide them in descending order (eg week,day,hour; not hour,day,week)
 *
 * @param {Date} dateStart - date to compare to
 * @param {Date} dateEnd - second date, can be used as unit param instead
 * @returns {DateDifference }
 */
export function dateDiff(dateStart: Date, dateEnd: Date): DateDifference {
  let delta: number = Math.abs(dateStart.getTime() - dateEnd.getTime());
  return DATE_DIFF_KEYS.reduce<DateDifference>((res: DateDifference, key: DateDiffKey) => {
    res[key] = Math.floor(delta / DATE_DIFF_DEF[key]);
    delta -= res[key] * DATE_DIFF_DEF[key];
    return res;
  }, {} as DateDifference);
}