From 4a22d8345b43bd84b1f05a6b8f9468ed388fa349 Mon Sep 17 00:00:00 2001
From: sean <135666428+seantiz@users.noreply.github.com>
Date: Mon, 23 Jun 2025 18:01:43 +0100
Subject: [PATCH] docs: Add prominent link to svelte/reactivity from state

---
 documentation/docs/02-runes/02-$state.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/documentation/docs/02-runes/02-$state.md b/documentation/docs/02-runes/02-$state.md
index 8e6c91fad769..f9e647fb84e3 100644
--- a/documentation/docs/02-runes/02-$state.md
+++ b/documentation/docs/02-runes/02-$state.md
@@ -63,6 +63,12 @@ let { done, text } = todos[0];
 todos[0].done = !todos[0].done;
 ```
 
+### State for Collections
+
+Arrays aren't the only structure you might want to use when setting reactive state for a collection of items. The temptation is to reach for Javascript built-in classes like `Set`, `Map`, `URL` and wrap them in `state()`, but this approach won't work.
+
+Use Svelte's own reactive versions instead. You can import `SvelteSet`, `SvelteMap`, `SvelteURL` and other reactive classes in [`svelte/reactivity`](svelte-reactivity).
+
 ### Classes
 
 Class instances are not proxied. Instead, you can use `$state` in class fields (whether public or private), or as the first assignment to a property immediately inside the `constructor`: