// /**
//  * CountdownTimer class provides a simple countdown functionality that updates a display element on the page.
//  * It counts down from a specified end time and updates the UI every second.
//  *
//  * When the countdown reaches zero, it stops and displays "Time up!".
//  *
//  * @example
//  * // Usage:
//  * const countdown = new CountdownTimer(new Date('2024/01/01 00:00:00'), 'countdownDisplay');
//  */
// export default class CountdownTimer {
//     // The target end time for the countdown.
//     private endTime: Date;
//     // The HTML element where the countdown will be displayed.
//     private displayElement: HTMLElement;

//     /**
//      * Creates a new CountdownTimer instance.
//      *
//      * @param endTime - The date and time at which the countdown should end.
//      * @param displayElementId - The ID of the HTML element where the countdown should be displayed.
//      */
//     constructor(endTime: Date, displayElementId: string) {
//         this.endTime = endTime;
//         // Find the display element by its ID and ensure it's an HTMLElement.
//         const element = document.getElementById(displayElementId);
//         if (!element) {
//             throw new Error(`Element with ID ${displayElementId} not found.`);
//         }
//         this.displayElement = element;
//         this.startTimer();
//     }

//     /**
//      * Starts the countdown timer, updating the display every second.
//      *
//      * This method calculates the time remaining until the end time and updates the text content of the display element.
//      * If the countdown reaches zero, it stops and displays "Time up!".
//      *
//      * @private
//      */
//     private startTimer(): void {
//         const interval = setInterval(() => {
//             const remaining = this.endTime.getTime() - new Date().getTime();
//             if (remaining <= 0) {
//                 clearInterval(interval);
//                 this.displayElement.textContent = 'Time up!';
//                 return;
//             }
//             this.displayElement.textContent = this.formatTime(remaining);
//         }, 1000);
//     }

//     /**
//      * Formats the remaining time in milliseconds into a string in the format "HH:MM:SS".
//      *
//      * @param timeInMilliseconds - The remaining time in milliseconds.
//      * @returns A string representing the formatted time.
//      *
//      * @private
//      */
//     private formatTime(timeInMilliseconds: number): string {
//         const seconds = Math.floor((timeInMilliseconds / 1000) % 60);
//         const minutes = Math.floor((timeInMilliseconds / 1000 / 60) % 60);
//         const hours = Math.floor((timeInMilliseconds / 1000 / 60 / 60) % 24);

//         // Pad minutes and seconds with leading zeros for a cleaner display.
//         const formattedMinutes = minutes.toString().padStart(2, '0');
//         const formattedSeconds = seconds.toString().padStart(2, '0');
//         const formattedHours = hours.toString().padStart(2, '0');

//         return `${formattedHours}:${formattedMinutes}:${formattedSeconds}`;
//     }
// }

// Usage example:
// Create a new countdown timer that ends on January 1, 2024, at midnight,
// and updates the element with the ID 'countdownDisplay'.
// const countdown = new CountdownTimer(new Date('2024/01/01 00:00:00'), 'countdownDisplay');