debug-focused-element.js

function debugFocus(turnOn) {
  if (turnOn && window.debugFocusInterval) {
    console.log("debugFocus: already on");
    return;
  }

  if (!turnOn && !window.debugFocusInterval) {
    console.log("debugFocus: already off");
    return;
  }

  if (window.debugFocusInterval) {
    clearTimeout(window.debugFocusInterval);
    window.debugFocusInterval = null;
    console.log("debugFocus: off");
    return;
  }

  let activeElement = null;
  window.debugFocusInterval = setInterval(() => {
    if (activeElement != document.activeElement) {
      activeElement = document.activeElement;
      console.log("activeElement", activeElement);
    }
  }, 1000);
  console.log("debugFocus: on");
}