MutationObserver Javascript

var observer = new MutationObserver(function(mutations) {
  mutations.forEach(function(mutationRecord) {
    var id=mutationRecord.target.id;
    var inputW=mutationRecord.target.style.width;
    var inputH=mutationRecord.target.style.height;
    console.log(id, inputW+"/"+inputH);
  });    
});

  var target = document.getElementById(id);
  observer.observe(target, { attributes : true, attributeFilter : ['style'] });