(function(){
  const observe = function(element, callback, options = {childList: true, characterData: false, subtree: false, attributes: false, attributeFilter: undefined}){
    let observer = new MutationObserver(callback.bind(element));
    observer.observe(element, options);
    return observer;
  };
  let element = document.querySelector('');
  observe(element, function(records){

  });
})();