Explain generics and give a realistic use case.
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of TypeScript 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
Generics let you write code that works over many types while preserving the relationship between input and output types.
function first<T>(items: T[]): T | undefined {
return items[0];
}
const n = first([1, 2, 3]); // number | undefined
const s = first(['a', 'b']); // string | undefined
// constraint
function pluck<T, K extends keyof T>(items: T[], key: K): T[K][] {
return items.map((item) => item[key]);
}
Real use case: a typed API client or a React component that accepts a list and a render callback, so the callback parameter inherits the item type automatically.
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.