Edit in JSFiddle

let draggable = document.getElementById('draggable');

draggable.addEventListener('dragstart', (ev) => {
  ev.dataTransfer.setData('text/plain', null);
  ev.target.style.opacity = ".5";
});

draggable.addEventListener("dragend", (ev) => {
  ev.target.style.opacity = "";
});

let dropzones = document.querySelectorAll('.dropzone');
dropzones.forEach((dropzone) => {

  dropzone.addEventListener('dragenter', (ev) => {
    ev.preventDefault();
    dropzone.style.borderStyle = 'dashed';
    return false;
  });
  
  dropzone.addEventListener('dragover', (ev) => {
    ev.preventDefault();
    return false;
  });

  dropzone.addEventListener('dragleave', (ev) => {
    dropzone.style.borderStyle = 'solid';
  });

});
<div id="drag-container">
  <div class="dropzone">
    <div id="draggable" draggable="true">
      Drag Me
    </div>
  </div>
  <div class="dropzone"></div>
  <div class="dropzone"></div>
</div>
  #drag-container {
    display: flex;
    justify-content: space-between;
  }

  #drag-container > .dropzone {
    width: 150px;
    height: 150px;
    background: #dae8fc;
    padding: 10px;
    border: 1px solid #6c8ebf;
    display: flex;
    flex-direction: column;
    justify-content: center;
  }

  #draggable {
    width: 90px;
    height: 90px;
    line-height: 90px;
    text-align: center;
    background: #f8cecc;
    border: 1px solid #b85450;
    margin: 0 auto;
    cursor: pointer;
  }