ES7 Observe

var labelObj = {
  id: "dalabel",
  label: "",
  setLabel: function(label) {
    labelObj.label = label;
  }
};

var inputEl = document.querySelector("#dainput");

inputEl.addEventListener("keyup", function(e){
  labelObj.label = e.target.value;
});

Object.observe(labelObj, function(changes){
  changes.forEach(function(change){
    if (change.name == "label") {
      document.querySelector("#" + labelObj.id).innerHTML = change.object.label;
    }
  });
});