littlelink/app.js

// Set expanded value block to a variable
const valueBlock = document.getElementById("value-expanded");
const bodyTop = document.getElementById("top");

// Watch for the details element to be toggled
document.querySelector('.value-block').addEventListener('toggle', function() {
  if (this.open) {
    // Scroll to contents of value block when it is opened
    valueBlock.scrollIntoView({ behavior: "smooth" });
  } else {
    // Scroll to top of button list when value block is closed
    bodyTop.scrollIntoView({ behavior: "smooth" });
 }
});