Does FormData or serialize have filter-for-changed-elements only option?

[khpss]

Or if not, this would be a very welcome addition.

[claviska]

There's nothing like that built in, but we do expose getFormControls() from the same module that you can use to get all native and Shoelace form controls in a form. That combined with the defaultValue property could get you pretty close.

Is there a native counterpart to what you're asking for? I can't think of anything aside from comparing defaultValue to value.

[khpss]

No native counterpart, in the past I've written a couple different plain JS modules implementing this. There's actually two functions needed: one to gather values from the changed elements, and a second which is called only if the Fetch or AJAX succeeds, which updates defaultValues (or the equivalent) to match values.

It does seem like such an obvious operation: just show me what's changed--that's all I want to PATCH.

[khpss]

Another benefit of the changed-values only is that -- without having to somehow implement a complete undo stack -- you can do nothing if the values have been fiddled with by the users but have ended up back at their original state. ('Nothing' as far as transacting with the server, you'd still want to disable the "save" button if that's tracking whether any data values have been changed.)

[claviska]

Got it. It definitely feels more like a framework feature, but definitely handy. Since Shoelace form controls mimic native form controls, I think you'll have luck comparing defaultValue to value, which is the only way I can think to do it without brute force serializing and then diffing it.