What is the "readonly" modifier in TypeScript, and how does it affect properties and arrays?
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
The "readonly" modifier in TypeScript is used to make properties or array elements read-only, meaning they cannot be modified once initialized. It provides a way to enforce immutability and prevent accidental modifications to certain values. When applied to properties, it prevents reassignment, and when applied to arrays, it disallows adding or removing elements after initialization.
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.