bookmarklet - adds a black div as overlay

overlay.js

// add layer
javascript:(
  function() {
    var div = document.createElement('div');
    var w = window.innerWidth;
    var h = window.innerHeight;
    div.setAttribute("class", "black-overlay");
    div.setAttribute("style", "position: fixed; top: 0px; left:0px; width: "+w+"px; height: "+h+"px; background-color: rgba(0,0,0,0.3); pointer-events: none; z-index: 4294967296");
    document.body.appendChild(div);
  }
)();

// remove layer
javascript:(
  function() {
    o = document.getElementsByClassName('black-overlay');
    document.body.removeChild(o[0]);
  }
)();