function setupQuoteApp() {
  ... 
  // Note: 
  // Variable/constant declarations + function definition can also be placed
  // in the outer scope or in a separate scope.
  let autoplayInterval = null;
  function toggleAutoPlay() {
      if (autoplayCheckbox.checked) {
        autoplayInterval = setInterval(pickFromArray, 5000);
        autoplayStatus.textContent = "Auto-play: ON";
        autoplayStatus.style.color = "#4CAF50";
      } else {
        clearInterval(autoplayInterval);
        autoplayInterval = null;
        autoplayStatus.textContent = "Auto-play: OFF";
        autoplayStatus.style.color = "brown";
      }
  }

  // Code that runs when the page loads -- easier to read
  autoplayCheckbox.addEventListener("change", toggleAutoPlay);
  button.addEventListener("click", pickFromArray);

  pickFromArray();
}