Get Date diff (sec, min, hours) like moment.diff with Vanilla JS

datediff.ts

const SECONDS = 1000;
const MINUTES = SECONDS * 60;
const HOURS = MINUTES * 60;

interface Result {
  hours: number;
  minutes: number;
  seconds: number;
}

function dateDiff(d1: Date, d2: Date): Result {
  const diff = Math.abs(Number(d1) - Number(d2));

  const hours = Math.floor(diff / HOURS);
  const minutes = Math.floor((diff - hours * HOURS) / MINUTES);
  const seconds = Math.floor(
    (diff - (hours * HOURS + minutes * MINUTES)) / SECONDS
  );

  return {
    seconds,
    minutes,
    hours,
  };
}

// Test
const TEST_DATA = [
  {
    d1: new Date("2020-01-02T10:00:00"),
    d2: new Date("2020-01-02T10:00:30"),
    results: { seconds: 30, minutes: 0, hours: 0 },
  },
  {
    d1: new Date("2020-01-02T10:00:00"),
    d2: new Date("2020-01-02T10:10:30"),
    results: { seconds: 30, minutes: 10, hours: 0 },
  },
  {
    d1: new Date("2020-01-02T10:00:00"),
    d2: new Date("2020-01-02T12:00:30"),
    results: { seconds: 30, minutes: 0, hours: 2 },
  },
  {
    d1: new Date("2020-01-02T10:00:00"),
    d2: new Date("2020-01-03T10:00:00"),
    results: { seconds: 0, minutes: 0, hours: 24 },
  },
  {
    d1: new Date("2020-01-02T10:00:00"),
    d2: new Date("2020-01-03T11:20:10"),
    results: { seconds: 10, minutes: 20, hours: 25 },
  },
  {
    d1: new Date("2020-01-02T10:00:00"),
    d2: new Date("2020-01-03T10:01:22"),
    results: { seconds: 22, minutes: 1, hours: 24 },
  },
];

function assertResult(actual: Result, expected: Result): boolean {
  return (
    actual.seconds === expected.seconds &&
    actual.minutes === expected.minutes &&
    actual.hours === expected.hours
  );
}

let i = 0;
for (const { d1, d2, results } of TEST_DATA) {
  const ret = dateDiff(d1, d2);
  if (assertResult(ret, results)) {
    console.log(`SUCCESS: ${i}`);
  } else {
    console.error(
      `FAILED: ${i}, seconds=${ret.seconds}, minutes=${ret.minutes}, hours=${ret.hours}`
    );
  }

  i++;
}