Sharing behaviour.
WHAT A COMPOSABLE IS
A function encapsulating reactive logic, usable across components.
WHAT IT REPLACES
Mixing shared behaviour into components in ways that obscure its origin.
WHAT TO PUT IN ONE
State and logic belonging together: a data fetch, a form, a subscription, a browser API.
WHAT MAKES A GOOD ONE
One clear purpose Returns what the component needs Cleans up after itself
WHY CLEANUP MATTERS
Listeners and timers otherwise accumulate.
WHAT NAMING CONVENTION TO FOLLOW
The established prefix, so their nature is obvious.
WHAT TO AVOID
Composables doing several unrelated things Hidden dependencies on component context Shared state where local state was intended
THAT LAST POINT
State defined outside the composable function is shared by every caller, which is sometimes intended and frequently not.
WHAT TO ESTABLISH
Whether state should be per-instance or shared.
WHAT TO TEST
Composables independently, since they are plain functions.
