Today I’d like to talk about native Drag&Drop using HTML5. I know this is a functionality you’ll seldom use, but depending on the UI you’re creating, it might come quite handy. For instance, the Editorial Calendar included in Nelio Content makes an extensive use of such a feature:
As you can imagine, rescheduling posts should be as simple as dragging and dropping them around the calendar, right? And that’s exactly what Nelio Content‘s calendar does! But how? How do you implement this? How do you specify which elements should move? How do you tell the browser which elements can receive a drop? Well, that’s what we’ll be talking about right now!
Drag & Drop Using jQuery UI
droppable. The former is applied to the element we want to drag, and the latter is used to the elements in which we should be able to drop what we’re dragging. Let’s take a look at the following running example to have a better understanding of what I’m talking about:
draggable. The function we call accepts an object with several properties but we’re only using one: the
helper. By using
helper:"clone", we’re basically telling jQuery UI that, when we start to drag an item, the “element” that we’ll be moving around will be a clone of the original item.
Next, we simply specify that all elements with the class
day are droppable areas–that is, they can receive a drop event and respond to it as we please. In this particular example, we configured the droppable area as follows: first, we tell jQuery that we’ll be only accepting elements with the
item class; then, we specify the class that a droppable area must have when we’re hovering it while dragging an element (so that we can highlight it and let the user know they can drop the element there); and finally we define the drop function, which tells our UI how to behave when we drop an element (in this case, we remove the dragged object from the original location to the area in which we dropped it).
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- Specify what can be dragged. That’s super simple–we only need to add the
- Specify where can an element be dropped. We simply need to specify the
ondropcallback of the droppable elements.
And that’s it! Here you have the native implementation:
“Hold on a sec, David. That’s way more complicated than what you’ve just explained.” Well, yes, you’re right: implementing a native D&D solution requires a few more lines of code than those required by jQuery UI, because some of the things that can be tweaked using a simple flag in jQuery, require a tiny function in vanilla JS. Let’s take a closer look:
- The helper we’re dragging. Remember the helper option in jQuery UI? Well, we need something similar in HTML5. When we start to drag something, the callback
ondragstartis called and it’s our responsibility to define the helper element (lines 9 and 10) and store the element we’re moving in a global variable (line 11).
- Highlight droppable areas. To highlight the droppable areas when hovering them with the mouse, we need to use three low level events:
ondragleave. With these, we can easily add or remove the
highglightclass as we please.
And that’s all! Indeed, native Drag & Drop is more verbose, but the final result is faster and feels more smooth. In this particular example you might not feel the difference, but if you’re running it on an old computer or if there’s plenty of rendered elements on the screen, there’s a huge difference.