Switch statements are fine for simple tasks like the one in the example, especially earlier in a project where you do not know what you need in the future. You can always switch it to the correct pattern in version 2 as that way its better understood what hidden needs the code in question has, thus making it easy to pick a good OOP patern to replace it.

Then again, my jugment might be colored by working on codebases that are >21 years old.

It's however easy to read and that feels good if not right, since the common solutions to this imagined problem require substantial mental overhead as seen on https://hackernoon.com/rethinking-javascript-eliminate-the-s.... To promote "single functions" we could:

  handleEvent(e) {
    this[e.type](e, e.target);
  }
  mousemove(e, elm) {
    elm.style.left = e.clientX + 'px';
  }

... but then the discussion would almost certainly revolve around this questionable decision instead of the original topic.

> No, that a switch statement is more verbose than a single function.

You're vacillating and applying an inconsistent standard. The switch statement is used where multiple listeners are being attached, therefore it wouldn't work with your "single function". You'd need multiple functions.

Give any example passing functions directly as the callback to `addEventListener` to demonstrate your case, please. The equivalent version that simply implements DOMEventListener will be less verbose, be lighter on resources (both with memory use and with runtime), and have no need for any this-binding workaround weirdness.