Vanilla JavaScript Drag n Drop

How cool are drag and drop editors, right?
Ever wondered how much space ship engineers you need to create one from scratch?
Let me help you: zero, everyone can build one, and only using these three things; HTML, CSS, Vanilla JavaScript.

Let me first explain what we are going to make. We will make a template builder, so we will have blocks on the left side, which are our building blocks. \
Then on the right, we have our editor view. We can drag these building blocks onto our editor.
Once we drag an element, we will make it appear differently.
The actual content of our blocks will be placed in a hidden div.

HTML Structure

First we will build our HTML structure:

<div class="container">
  <div class="col col-3">
    <div class="comp-holder">
      <div
        data-table="comp-01"
        class="comp js-draggable"
        draggable="true"
        ondragstart="onDragStart(event);"
        ondragend="onDragEnd(event);"
      >
        [Header component]
      </div>
      <div
        data-table="comp-02"
        class="comp js-draggable"
        draggable="true"
        ondragstart="onDragStart(event);"
        ondragend="onDragEnd(event);"
      >
        [Image component]
      </div>
      <div
        data-table="comp-03"
        class="comp js-draggable"
        draggable="true"
        ondragstart="onDragStart(event);"
        ondragend="onDragEnd(event);"
      >
        [Text component]
      </div>

      <div
        data-table="comp-04"
        class="comp js-draggable"
        draggable="true"
        ondragstart="onDragStart(event);"
        ondragend="onDragEnd(event);"
      >
        [Footer component]
      </div>
    </div>
  </div>
  <div class="col col-9">
    <h3>Dropzone</h3>
    <div
      id="dropzone"
      class="editor-view"
      ondragover="onDragOver(event);"
      ondrop="onDrop(event);"
    ></div>
  </div>

  <div class="hidden">
    <header class="actual-comp" id="comp-01">
      <a href="https://daily-dev-tips.com">
        <img src="https://daily-dev-tips.com/images/logo.png" height="50" />
      </a>
      <a href="#">Menu</a>
    </header>
    <div class="actual-comp" id="comp-02">
      <img
        class="image"
        src="https://images.unsplash.com/photo-1587588354456-ae376af71a25?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1950&q=80"
      />
    </div>
    <div class="actual-comp" id="comp-03">
      <p class="text">
        Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer quis cursus
        massa, eget fringilla dolor. Praesent ligula libero, luctus sit amet urna a,
        semper scelerisque lorem. Curabitur efficitur, tortor in tempor elementum, orci
        quam mollis quam, nec fermentum lacus mauris eu nisl. Praesent elementum eros et
        justo faucibus, sed vestibulum mauris tincidunt. Aenean suscipit ultrices tellus,
        at aliquam diam. Class aptent taciti sociosqu ad litora torquent per conubia
        nostra, per inceptos himenaeos. Vivamus non maximus mauris, nec finibus risus.
        Donec sit amet massa malesuada, mollis mi nec, condimentum justo. Pellentesque
        velit ligula, feugiat eget nisi quis, mattis eleifend sem. Proin pretium risus
        ligula, a aliquet elit commodo sit amet.
      </p>
    </div>
    <footer class="actual-comp" id="comp-04">&copy; Daily Dev Tips 2020</footer>
  </div>
</div>

The important part here is the component structure:

<div
  data-table="comp-01"
  class="comp js-draggable"
  draggable="true"
  ondragstart="onDragStart(event);"
  ondragend="onDragEnd(event);"
>
  [Header component]
</div>

We make this draggable (this is a html element property) and add ondragstart and ondragend functions which we will create in our JavaScript.

Then we tell our editor it can accept draggable elements to be dropped on it.

<div
  id="dropzone"
  class="editor-view"
  ondragover="onDragOver(event);"
  ondrop="onDrop(event);"
></div>

Here we stop the default behaviour by overwriting the onDragOver function and we include a onDrop function which we will call in our JavaScript.

CSS Setup

We will need to incorporate some CSS to make the layout fixed so let's start with the basic CSS:

.container {
  min-height: 100vh;
  display: flex;
  padding: 1rem;
  .col {
    padding-right: 0.5rem;
    padding-left: 0.5rem;
  }
  .col-3 {
    flex-basis: 25%;
  }
  .col-9 {
    flex-basis: 75%;
    h3 {
      text-align: center;
      margin-bottom: 0.5rem;
    }
  }
  .editor-view {
    border: 2px dotted #efefef;
    min-height: 400px;
    width: 100%;
  }
}
.comp {
  background: teal;
  height: 50px;
  margin-bottom: 0.5rem;
  display: flex;
  justify-content: center;
  align-items: center;
}
.hidden {
  display: none;
}

We are using flex box here to make this simple and just create a 1/4 - 3/4 column layout.
Then we give it some basic styling to show off what we can use.

Now let's move into the fun part, JavaScript!

JavaScript for our Drag N Drop editor

function onDragStart(event) {
  event.dataTransfer.setData('text/plain', event.currentTarget.dataset.table);
  event.currentTarget.style.backgroundColor = 'yellow';
}

So when we start dragging our components we can use the dataTransfer API to set certain data on our component, in this case we are setting our custom dataset attribute (remember the data-table="comp-01".
We then set the element to have a different color so we can see we picked it up.

function onDragEnd(event) {
  event.currentTarget.style.backgroundColor = 'teal';
}

When we stop dragging the element the onDragEnd event will be called, in this case we use this to return the color back to it's original.

function onDragOver(event) {
  event.preventDefault();
}

The above function gets called when we drag over our editor and we prevent any default events here.

const dropzone = document.getElementById('dropzone');

function onDrop(event) {
  let id = event.dataTransfer.getData('text');

  const draggableElement = document.getElementById(id);
  const clone = draggableElement.cloneNode(true);

  dropzone.appendChild(clone);

  event.dataTransfer.clearData();
}

Then, once we drop our element, we need to get the data we set in the onDragStart event function. We again use dataTransfer api to get data that will return the data id.
We then find the original content (which sits in our hidden div) and clone it, because we might want to use it more often.
We then say dropzone, append a child who is the cloned element.
Voila, we added a clone to our editor.
We then clear our the data set on our dropped element.

Have a view and play around on Codepen.

See the Pen Vanilla JavaScript Drag 'n Drop by Chris Bongers (@rebelchris) on CodePen.

Or download the code on GitHub

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