preventing drag & drop disaster

prevent_drag_drop.js

// preventing drag & drop disaster
var preventDrag = function(e) {
  e.stopPropagation();
  e.preventDefault();
};
var preventDrop = function(e) {
  if (e.dataTransfer.files.length > 0) {
    e.stopPropagation();
    e.preventDefault();
  }
};
window.document.addEventListener('dragenter', preventDrag, false);
window.document.addEventListener('dragover', preventDrag, false);
window.document.addEventListener('drop', preventDrop, false);