Click Outside Detector

Celý článek

It’s a reasonable UX thing that you can click-to-open something, and then not only be able to click that same thing to close it, but click outside the thing that it opened to close it. Kitty Giraudel just blogged about that. The trick is that once the thing is opened, you attach an event handler to the window with that watches for events (like another click). If that subsequent click did not happen within the newly-opened area, close it. Like, literally thing.contains(event.target). It’s a nice trick, I think.

There are lots of little things to think about though. For example:

we have to stop the propagationg of the click event on the toggle itself. Otherwise, it goes up to the window click listener, and since the toggle is not contained within the menu, it would close the latter as soon as we try to open it.

Right right. Can’t have that or it breaks the whole thing.

We have this same pattern in a lot of places on CodePen. Like Kitty, we have it implemented in React. In taking a peak at our implementation, it’s got a number of bells-and-whistles I figured were worth mentioning. For example, ours isn’t a function or hook, but a component wrapper we use like:

<ClickOutsideDetector 
  listen 
  onClickOutside={() => { closeTheThing(); }}
>
  A Menu or Modal or something.
</ClickOutsideDetector>

That way it is a generic wrapper that we can use for anything on a “click outside”. The bells-and-whistles being:

• You can pass in component prop so that it doesn’t have to manifest as a <div> but whatever you want it to be semantically.
• The listen prop allows you to toggle if it is currently actively listening to events. Like a quick way to short-circuit it.
• An ESC keypress is the functional equivalent to clicking outside.
• Handles touch events as well as clicks
• Handles a case where the click outside happens into an <iframe> in which case the window has a blur event rather than a click.
• Allows you to pass in elements to ignore, so rather than the stopPropagation trick that Kitty documented, we can be specific about elements that don’t trigger a click outside.

So many little things! To me this is the kinda perfect little example of real-world development. You just want one little behavior and ultimately there are a ton of considerations and edge cases you have to deal with and it’s never really done. I just touched our component in the last few months because of a third-party tool we used changed how they did something which affected iframes in use on the page. Ultimately I had to watch for a blur event that then check the classList of document.activeElement to see if that was the thing eating the click outside!

Annnnyway, I tossed up a only-slightly-dumbed-down version of ours here.

And I saw something from Kitty’s post that we weren’t handling, and it’s in the very first sentence:

we needed a way to close the menu when clicking outside of it or tabbing out of it.

Emphasis mine. Don’t worry, I’ve got a TODO in our code for that now.

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