I've recently been looking at retrofitting keyboard navigation support to JS Bin, but I was immediately struck by the totally lack of visibility on what was in focus.

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Sure, this is a short-coming of the original design and bad choises I had made with JS Bin's code base. Perhaps you can see from the animation below, when the body is in focus, tabbing is focusing something but until I actually tab to the "HTML" panel title, there's no visual feedback as to what I should be fixing:

Tab focusing is clueless

If you can see it, the browser's status bar tells me that I'm moving focus, but it's near impossible to work out which element I'm working with.

So I built a mini utility to visualise what's happening. Now with that utility:

Tabbing visible

Installation

Either add the code directly to your project as a debug dependancy, or use it as a snippet in your devtools:

(function () {
  var active = document.createElement('pre');
  document.body.appendChild(active);
  active.tabindex = -1;
  with (active.style) { // warning: `with` I know what I'm doing!
    position = 'fixed';
    padding = '2px';
    bottom = right = '20px';
    margin = 0;
    fontSize = 12;
    color = '#fff';
    background = '#aaa';
    whiteSpace = 'pre-wrap';
    maxWidth = '95%';
  }

  var lastActive = null;
  var showActive = function () {
    var el = document.activeElement;
    var html = '';
    var attrs = el.attributes;
    var i = 0;

    if (el !== lastActive && el !== active) {
      for (; i < attrs.length; i++) {
        html += ' ' + attrs[i].name + '="' + attrs[i].value + '"';
      }

      active.textContent = '<' + el.nodeName.toLowerCase() + html + '>';
      lastActive = el;
    }

    requestAnimationFrame(showActive);
  };

  showActive();
})();

Here's a live demo:

JS Bin

So now I have visibility on what is being focused, I can fix various issues ranging from outline being removed, only including :hover styles and not :focus and applying proper menu logic to menu-like objects.