countdown timer app code

Modular Countdown Timer

Every frontend developer needs a reliable toolkit of lightweight, dependency-free utilities, and this plug-and-play countdown timer is a perfect addition. By encapsulating the logic, presentation, and configuration into a single standalone file, it completely bypasses the overhead of heavy frameworks or clunky third-party plugins.

Because it targets a simple hook identifier, you can drop the script into landing pages, promotional banners, or maintenance screens in seconds and configure the duration directly in the markup. It is an efficient, highly portable solution for fast-paced deployment workflows where maintaining speed, clean source code, and absolute control over the DOM is paramount.

<div id="countdown-timer"></div>
    
    <script>
      (function () {
        const hours = 1;
        let totalSeconds = hours * 3600;
        const target = document.getElementById("countdown-timer");
    
        target.style.cssText =
          "font-family: sans-serif; font-size: 2em; font-weight: bold;";
    
        function updateDisplay() {
          const h = Math.floor(totalSeconds / 3600);
          const m = Math.floor((totalSeconds % 3600) / 60);
          const s = totalSeconds % 60;
    
          target.textContent =
            `${String(h).padStart(2, "0")}:` +
            `${String(m).padStart(2, "0")}:` +
            `${String(s).padStart(2, "0")}`;
        }
    
        updateDisplay();
    
        const interval = setInterval(function () {
          totalSeconds--;
    
          if (totalSeconds <= 0) {
            totalSeconds = 0;
            clearInterval(interval);
          }
    
          updateDisplay();
        }, 1000);
      })();
    </script>
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