Dependencies and Effect Behavior
Explore how React's dependency array controls when effects run in functional components. Understand how to manage dependencies correctly to prevent infinite loops, stale data, and excessive executions, ensuring your effects stay synchronized with state and props for predictable component behavior.
Once we understand that effects run after rendering, the next question becomes more precise. When exactly should an effect run again? This is where the dependency array becomes central. It is not just a syntax detail. It is a way of describing how our effect relates to the state and props over time. If we misunderstand dependencies, we often create effects that run too often, not often enough, or even infinitely. To avoid this, we need a clear mental model of what the dependency array represents.
What the dependency array means
The dependency array tells React when an effect should re-run. More specifically, it lists the values that the effect depends on. React compares each value in the array between renders. If any value changes, the effect runs again. If none of them change, the effect is skipped. The cause is a change in one of the dependencies. The ...