Duration.js

Object.defineProperty(Number.prototype, "milliseconds", {
  get() {
    return this / 1000;
  },
  configurable: true,
});
Object.defineProperty(Number.prototype, "seconds", {
  get() {
    return this;
  },
  configurable: true,
});
Object.defineProperty(Number.prototype, "minutes", {
  get() {
    return this * 60;
  },
  configurable: true,
});
Object.defineProperty(Number.prototype, "hours", {
  get() {
    return this * 60 * 60;
  },
  configurable: true,
});
Object.defineProperty(Number.prototype, "days", {
  get() {
    return this * 60 * 60 * 24;
  },
  configurable: true,
});

// Use it like this
(3).milliseconds; // => 0.003
(3).seconds; // => 3
(3).minutes; // => 180
(3).hours; // => 10_800
(3).days; // => 259_200