Lesson 03 · React
Effects, Lists & Forms
Effects connect rendering to the world outside it - timers, subscriptions, page titles - with cleanup functions and dependency arrays. Then controlled forms and derived lists: the two jobs that look like effects but are not.
Prerequisites: State: When a Component Remembers
Learning objectives
By the end of this lesson, you will be able to:
- Decide whether a job belongs to an effect, to state, or to calculation during render
- Write effects with a cleanup function and the dependency array that matches what they read
- Build controlled forms, one state field per input or a single state object for many
- Render derived lists by filtering data during render and mapping it with stable keys