purify.js

javascript: (function(doc) {
  var add = doc.addEventListener;
  add('mouseover',overHandler,false);
  add('mouseout',outHandler,false);
  add('click',clickHandler,false);
  add('keypress',keyHandler,false);
  function removeListeners(){
    var rm = doc.removeEventListener;
    rm('mouseover',overHandler,false);
    rm('mouseout',outHandler,false);
    rm('click',clickHandler,false);
    rm('keypress',keyHandler,false);
  }
  var theElm;
  function overHandler(e){
    theElm = e.target;
    addBG(theElm);
  }
  function outHandler(e){
    removeBG(theElm);
  }
  function clickHandler(){
    removeBG(theElm);
    killOthers(theElm);
    removeListeners();
  }
  function addBG(elm){
    var st = elm.style;
    if(st.backgroundColor)st.origBG = st.backgroundColor;
    st.backgroundColor = 'orange';
  }
  function removeBG(elm){
    if(!elm)return;
    var st = elm.style;
    st.backgroundColor = st.origBG||'';
    st.origBG=null;
  }
  function keyHandler(e){
    try{Hash[e.keyCode||e.which](e)&&e.preventDefault();}catch(e){}
  }
  var Hash = {
    27:function(){removeBG(theElm);removeListeners();return true}/*Esc*/
    ,38:function(){if(theElm!=doc.body){removeBG(theElm);theElm=theElm.parentNode;addBG(theElm);}return true}/*up*/
    ,13:function(){clickHandler();return true;}/*Enter*/
  };
  function killOthers(ele){
    while(ele!=doc.body){
      [].forEach.call(ele.parentNode.childNodes,function(e){if(e!=ele && e.style)e.style.display='none'});
      var st = ele.style;
      st.width='100%';
      st.padding=st.margin=0;
      ele=ele.parentNode;
    }
  }
})(document);