What does the dependencies array in useEffect control?

What does the dependencies array in useEffect control?

• A. It determines when the effect re-runs (e.g., [] runs once).
• B. It defines the cleanup logic to run after unmount.
• C. It specifies the DOM elements the effect will touch.
• D. It sets the initial state of the component.

Answer: (A)

The dependencies array controls when the effect re-runs. React watches the values you put in that array and re-executes the effect only if any of them changed since the last render. If you provide an empty array, the effect runs once after the initial render. If you omit the array altogether, the effect runs after every render. The other behavior you might be thinking of—cleanup when unmounting or before the next run, or touching specific DOM elements—is handled by the code inside the effect itself, not by the dependencies list.

The dependencies array controls when the effect re-runs. React watches the values you put in that array and re-executes the effect only if any of them changed since the last render. If you provide an empty array, the effect runs once after the initial render. If you omit the array altogether, the effect runs after every render. The other behavior you might be thinking of—cleanup when unmounting or before the next run, or touching specific DOM elements—is handled by the code inside the effect itself, not by the dependencies list.