Subscribe to Store

Watches specific keys in a named global store and signals when they change, with the previous value alongside the new one.

Subscribes to a store and fires only for the keys named in Keys, so a component that cares about one field is not woken by every unrelated write. Leaving Keys empty watches the whole store. Both Value and Previous Value update before changed fires, so a handler can compare them. Notifications arrive once per commit in subscriber registration order; a write that sets a key to the value it already held is not a change and fires nothing. Changing Store Name or Keys moves the subscription rather than adding a second one, and deleting the node removes it — a disposed node leaves no subscriber behind, which matters because a store outlives the components that read it.

When to use it

Reacting to shared state changing, rather than rendering it. To display a value, wire Global Store's state straight into the UI; use Subscribe when something must happen on a change — refetch, animate, navigate, log. Prefer naming Keys over watching everything, so unrelated writes do not trigger work.

At a glance

Category	Data
Type name	net.noodl.GlobalStore.Subscribe
Available in	browser
SSR compatibility	safe
Provided by	noodl-runtime

Inputs

Values

Name	Type	Default	Description
keys	String	—	Comma-separated keys to watch; leave blank to react to every change in the store
storeName	String	app	Names the store to watch; must match the Store Name of the Global Store node that owns it

Outputs

Values

Name	Type	Default	Description
changedKeys	String	—	Comma-separated keys that changed in the notification that fired Changed
previousValue	*	—	The same projection as Value, as it was immediately before the change that fired Changed
value	*	—	The watched value: one key gives that key, several give an object of just those keys, none gives the whole store

Signals

Name	Type	Default	Description
changed	Signal	—	Fires when one of the watched keys changed, and not for a commit that touched only other keys

Patterns

• Name the keys you care about instead of leaving Keys empty, so a busy store does not wake every component on every write.
• Compare previousValue with value to react to a specific transition — signed-out to signed-in — rather than to any change at all.
• Global Store state for rendering; Subscribe changed for side effects. Using Subscribe to drive display work is usually a sign the state should simply be wired in.

Watch out for

• Watching the whole store to react to one key: every unrelated write then does that component's work again.
• Expecting one notification per key when several were written in a batch — a batch is one commit, and changedKeys names all of them.
• Holding previousValue as a history. It is only the value immediately before this change; the State History node keeps a real history.

Examples

Shared state: one store read by two unrelated components

Two components that are not parent and child, sharing state through a named store instead of prop drilling or a Send/Receive Event pair. Sign In writes user with Set Global Store; Header declares the same store by name and renders state — no wiring runs between the two components, because naming the store is what connects them. Header also subscribes to just the user key, so a write to any other key does not wake it, and uses previousValue against value to fire only on the signed-out → signed-in transition rather than on every change. Initial State fills gaps without overwriting live state, so Header remounting cannot reset a store Sign In is already using.

Related nodes

Global Store, Set Global Store, Variable

Generated

This page is generated from node-catalog-enriched.json. Do not edit it by hand — run npm run docs:nodes to regenerate, and fix the source enrichment instead.