Adds events in a backwards compatible way (legacy versions of IE).

on.js

(function(){
  Object.defineProperties(document, {
    "on": {
      value: function(evName, callback, useCapture){
        return addEvent.call(this, evName, callback, useCapture);
      }
    }
  });
  Object.defineProperties(window, {
    "on": {
      value: function(evName, callback, useCapture){
        return addEvent.call(this, evName, callback, useCapture);
      }
    }
  });
  window.elem = function elem(selector){ return document.querySelectorAll(selector); };
  Object.defineProperties(NodeList.prototype, {
    "each": {
      value: function(fn){
        var self = this;
        Array.prototype.slice.call(this, 0).forEach(function (){
          fn.apply(arguments[0], arguments);
        });
        return self;
      }
    },
    "on": {
      value: function(evName, callback, useCapture){
        this.each(function (elem){
          addEvent.call(elem, evName, callback, useCapture);
        });
        return this;
      }
    }
  });
  function addEvent(evName, callback, useCapture){
    if(this.addEventListener) this.addEventListener(evName, callback, useCapture || false);
    else if(this.attachEvent) this.attachEvent("on" + evName, callback);
    return this;
  }
})();