Explain all dependency array scenarios in the useEffect hook

Q: Explain all dependency array scenarios in the useEffect hook

No dependency array Empty dependency array Dependency array with values useEffect(() => { // This will run after every render }); useEffect(() => { // This will run once after the initial render }, []); useEffect(() => { // This will run after the initial render and every time `value` changes }, [value]);

Difficulty: 6/10

dependency array, stale closures, effect cleanup

The `useEffect` hook in React can be used to replicate the functionality of component lifecycle methods found in class-based components. By using different configurations of the `useEffect` hook, you can achieve the same effects as `componentDidMount`, `componentDidUpdate`, and `componentWillUnmount`. Here's how you can use `useEffect` to replicate the behaviour of these lifecycle methods:

1
No dependency array
2
Empty dependency array
3
Dependency array with values

No Dependency Array: When you don’t provide a dependency array, the useEffect hook will run after every render.

Empty Dependency Array: When you provide an empty dependency array, the useEffect hook will run once after the initial render, similar to componentDidMount in class components.

Dependency Array with Values: When you provide one or more values in the dependency array, the useEffect hook will run after the initial render and also every time any of those values change.

Scenario Questions

0-2 years experience

Follow-up Questions