Can useRef be used to store previous values?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of React conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
Yes, useRef is a common pattern when you want to compare current and previous props or state without causing re-renders.
Example: Storing previous state value
import { useEffect, useRef, useState } from 'react';
function PreviousValueExample() {
const [count, setCount] = useState(0);
const prevCountRef = useRef();
useEffect(() => {
prevCountRef.current = count;
}, [count]);
const prevCount = prevCountRef.current;
return (
<div>
<p>Current: {count}</p>
<p>Previous: {prevCount}</p>
<button onClick={() => setCount(c => c + 1)}>Increment</button>
</div>
);
}
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.