Is there a way to debounce a $derived()?

[frederikhors]

I tried with:

let searchText = $derived(debounce((typedText) => typedText, 2000)(typedText));

But searchText is not assigned!

1. Reproduction with $derived: searchText is not assigned.

2. Reproduction with $effect(): searchText assignment is not debounced at all:

   

[Antonio-Bennett]

Can you produce a repl

[frederikhors]

Yeah, here we go.

[frederikhors]

I added another reproduction with $effect too.

[7nik]

Such things are done via $derived.by because it allows to "initialize" the logic and return a value multiple times. REPL.

[julianjelfs]

Seems like this does not actually debounce the calling of the getter though. It just debounces the assignment of the result. If the getter itself is the expensive operation that we wish to debounce I'm not sure this helps. I have been trying to adapt what you have provided to achieve what I describe, but I either find that the getter is never called or it is called every time the dependency is updated which is (at least in my case) not addressing the problem.

[7nik]

yeah, because the effect needs to subscribe to the dependencies. You can avoid extra calls by passing deps explicitly.

[julianjelfs]

Ah right. I see. That's great. But it doesn't seem to work if the dependency is an object and I have changed one of the properties within it. In my case that's what I would want to do. e.g. I have an object that represents a form with a bunch of fields. I want the dependency to be the top level object and the effect to perform debounced validation of the object. This case still does not seem to work using the pattern you suggest. Is there any way to achieve what I'm going for?

[7nik]

You need to read all the props. For a one-level object it's just {...myObject}, for more deep ones - JSON.stringify(myObject) or $state.snapshot(myOjbect).

[julianjelfs]

OK - great thanks very much, that seems to be working.

[brunnerh]

Again, please stop cross-posting¹.
As I said before, you are evidently wasting people's time.

_{¹ https://stackoverflow.com/questions/78906849/is-there-a-way-to-debounce-a-svelte-5-derived-value, https://discord.com/channels/457912077277855764/1276579443871055934}