This is probably more for an ACF addon that a feature, but in order to add code associated with any ACF field, you have to add it to FUNCTIONS.PHP or a custom plugin.
I’d really love to see an additional section for each field that allows me to plug my code right into each individual field’s settings.
So, I can stick some JS code that handles validation or loading data from an external source, or updating other fields in the metabox.
For example, I have an ACF form for handling basketball brackets. And I’d like to display an update to the bracket in an HTML field each time a game is added. Right now, you have to add the game, update, then view the bracket on a front end page. Very time consuming.
It would also be nice to attach PHP code to a field that is executed each time the field is updated. Again, I can write code in my custom plugin, but maintaining it all gets to be a hassle when it would be so much easier if it were right there as an added section for each field.