Easy React Question 70 of 229

What is useEffect used for at a basic level?

Frontend Master · Speak this in 60–90 seconds · Faridabad & Delhi NCR

01234

Index starts at 0. Scan once for max — O(n).

UseEffect runs after paint for side effects: fetch, subscriptions, and syncing to document title.

Why interviewers care about React:

React questions separate people

who only read docs from people who shipped.

Keep it short, concrete,

and tied to Frontend work.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
UseEffect runs after paint
for side effects: fetch, subscriptions, and syncing to document title.
2
The dependency array controls
when it re-runs.
3
An empty array means
mount and cleanup on unmount, which is the mental model I start with.
4
Give an example
One tiny concrete case you can say aloud.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“The dependency array controls when it re-runs.”

Break into beats

Thedependencyarraycontrolswhenit

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

UseEffect runs after paint for side effects: fetch, subscriptions, and syncing to document title. The dependency array controls when it re-runs.