Bookmarklet to console log the active element on a timer

printFocusedElement.js

javascript: (() => {
  /*
   * This script is meant to be run as a JavaScript bookmarklet. "Install" it by pasting the script
   * into the URL field of a bookmark in your browser.
   * https://www.freecodecamp.org/news/what-are-bookmarklets/
   *
   * When invoked the first time, it will set a timer that prints the currently focused element to the
   * console every 2 seconds. When invoked again, it will cancel that timer, and will continue to
   * toggle the timer on each subsequent invocation.
   *
   * This is useful when trying to test keyboard navigation on a webpage, when some elements may not
   * have visible focus indicators or when the focus order isn't what was expected.
   *
   * The script stores the timer on the global variable `window.akInterval` or a different variable
   * of your choosing.
   */

  const intervalMillis = 2000;
  const globalVariableName = 'akInterval';

  if (window[globalVariableName]) {
    const intervalId = window[globalVariableName];
    clearInterval(intervalId);
    delete window[globalVariableName];
    console.log(`Stopped activeElement timer (interval ID ${intervalId})`);
  } else {
    const intervalId = setInterval(
      () => console.log(document.activeElement),
      intervalMillis
    );
    window[globalVariableName] = intervalId;
    console.log(
      `Started activeElement timer (every ${intervalMillis} ms, interval ID ${intervalId})`
    );
  }
})();

The timer approach has its advantages, but I just discovered that it's possible to listen to focus events so we can actually log the focused element as it changes. See https://hidde.blog/console-logging-the-focused-element-as-it-changes/