Extensions to the TypeScript Date class to work with diferences to a future date.

Date.ext.ts

export {};

/**
 * Extensions to the Typescript Date class.
 */
declare global {
  /**
   * Extension members declarations.
   */
  interface Date {
    /**
     * Returns time left from today to the date in milliseconds.
     */
    timeLeft(): number;
    /**
     * Check if current date already past the date or there are less than 24 hours left to it.
     */
    isLastDay(): boolean;
    /**
     * Returns the hours left to the date as extracted from
     * sentence like "There are hh:mm:ss left to the date".
     */
    hoursLeft(): number;
    /**
     * Returns the minutes left to the date as extracted from
     * sentence like "There are hh:mm:ss left to the date".
     * (NOT the total minutes)
     * To be used as a complement to `hoursLeft()`.
     */
    minutesLeft(): number;
    /**
     * Returns the seconds left to the date as extracted from
     * sentence like "There are hh:mm:ss left to the date".
     * (NOT the total seconds)
     * To be used as a complement to `minutesLeft()`.
     */
    secondsLeft(): number;
  }
}

Date.prototype.timeLeft = function (): number {
  return this.getTime() - new Date().getTime();
};

Date.prototype.isLastDay = function (): boolean {
  return this.timeLeft < 86400000;
};

Date.prototype.hoursLeft = function (): number {
  return Math.floor(this.timeLeft() / 3600000);
};

Date.prototype.minutesLeft = function (): number {
  return Math.floor((this.timeLeft() % 3600000) / 60000);
};

Date.prototype.secondsLeft = function (): number {
  return Math.floor((this.timeLeft() % 60000) / 1000);
};