Hasty Treat - JavaScript’s Drag and Drop API


In this Hasty Treat, Scott and Wes talk about JavaScript’s drag and drop API — how it works, concerns, best practices, and more!

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Show Notes

04:45 - What is it?

  • Drag and drop is really for desktop apps
  • You can drag and drop anything from any browser to any browser
  • The important thing here is that this is a set of browser standards that allow different apps to communicate

07:50 - How to implement

  1. Make an element draggable
  2. Listen on elements for drag events
    • The events bubble up, so you can listen on the parent element as items are added/removed

09:06 - DataTransfer API

  • You can store anything you want in it
  • getData / setData API
  • Reference strings

11:35 - Accepting drops

  • When you dragOver, you need to preventDefault()
  • Calling the preventDefault() method during both a dragEnter and dragOver event will indicate that a drop is allowed at that location

13:01 - Drop Image

  • Set whatever you want

16:00 - Drop Effect

  • What does it look like when you drop it? Does it go back?
  • dataTransfer.effectAllowed
  • e.dataTransfer.setDragImage(nothing, 0, 0);

18:02 - Security concerns

20:34 - Shortcomings:

  • Edge cases out the WAZOO
    • Margin caused dragout events
    • Lots of if statements
  • It’s up to you to do EVERYTHING
    • CSS, classes, hover styles, etc.
  • Accessibility
    • Inaccessible by default, unless using mouse keys
    • Have to announce everything
  • Mobile

26:14 - Lbs

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