How do you properly set dependencies for useEffect?

Properly defining the dependency array in the useEffect hook is the key to stable application performance and avoiding elusive bugs. The main rule here is that absolutely every variable, function, or object from the component's scope used inside the effect body must be included in this array. If this rule is neglected, React will continue to use stale closures with values from past renders, leading to outdated data in the interface.

To ensure compliance with this rule, developers actively use the built-in eslint-plugin-react-hooks linter, which automatically highlights omissions and suggests fixes. It is strongly discouraged to disable this rule using comments like disable-next-line unless absolutely necessary. If the linter complains about a variable, it means the effect's logic is structured in such a way that it should respond to its changes.

Functions declared inside the component and passed as dependencies to the effect often present a particular difficulty. Since a new reference to the function is created on every new render of the component, the effect will trigger constantly, causing infinite loops of requests or updates. To solve this problem, the useCallback hook is used, which memoizes the function and preserves the stability of its reference between renders until its own dependencies change.

A similar situation arises when working with complex objects or arrays passed into the effect. To prevent unnecessary effect triggers caused by an object being recreated with the same properties, the useMemo hook is applied. It allows caching the object value and updating it only when the underlying primitive data actually changes.

If during development you find that an effect requires too many dependencies or starts to seem too noisy and overloaded, this is a clear signal to rethink the component architecture. Often the problem can be solved by splitting one large effect into several small, highly specialized effects, each responsible strictly for its own task, or by extracting complex logic into an external custom hook.