Why Doesn't My React setInterval Update State Correctly?

React State Hook and setInterval: A Closer Look

When utilizing React state hooks within setInterval, it's important to address a common caveat. In some cases, the state may not update as expected beyond the initial render.

Understanding the Issue

The crux of the problem lies in the closure captured by setInterval. The callback function provided to setInterval has access to the initial state value at the time of rendering. However, subsequent renders do not invoke useEffect(), leaving the callback function with an outdated state value. This causes time to remain at 0 within the setInterval callback.

Solution: Leverage the State Callback Form

To resolve this issue, employ the second form of state hooks, which accepts a callback. This callback receives the current state as an argument. By leveraging this form, you can access the most recent state value before incrementing it.

setTime(prevTime => prevTime + 1); // Corrected version

Additional Insights

For further exploration, Dan Abramov's insightful blog post offers alternative approaches to tackling this problem. We highly recommend delving into it for a deeper understanding.

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