What types of values can `useState` hold?
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
The useState hook accepts different types of values.
- Primitives:
number,string,boolean - Arrays
- Objects
- Functions
nullorundefined
But you needs to be cautious with reference types (objects/arrays) because React compares old and new values by reference, so direct mutations won't trigger a re-render.
For example, the correct and wrong ways of state updates as shown below,
user.name = "Sudheer"; //wrong way
setUser(prev => ({ ...prev, name: 'Sudheer' })); //correct way
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.