TypeScript Interview
TypeScript vs JavaScript Comparison Questions
Explain technical differences between TS and JS, type erasure, and structural compilation.
Last Updated: July 29, 2026
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10 min read
Interviewers frequently probe your understanding of the relationship between TypeScript and JavaScript: compilation vs interpretation, type erasure, and prototype mechanics.
1. Introduction & Architecture
2. Deep Dive & Core Concepts
Key Comparison Technical Points: 1. Type Erasure: TypeScript types generate ZERO JavaScript code. Types are stripped completely during compilation. 2. Structural vs Nominal: JS has dynamic runtime objects; TS uses compile-time structural duck-typing. 3. Execution Environment: Browsers and Node.js execute JavaScript, not TypeScript directly.
3. Basic Code Example
4. Advanced Production Patterns
5. Interactive Code Playground
console.log("TypeScript compiles down to clean standard JavaScript.");6. Common Pitfalls & Edge Cases
Note: Except for Enums, Namespaces, and Class Parameter Properties, TypeScript features do NOT emit any runtime code.
7. Interview Q&A & Quizzes
Q: Does TypeScript add any runtime overhead to JavaScript applications?
A: No. TypeScript types are erased during compilation, so the emitted JavaScript runs with identical runtime performance.
8. Summary Comparison Table
| Aspect | JavaScript | TypeScript |
|---|---|---|
| Type System | Dynamic (Runtime) | Static (Compile-time) |
| Execution | Native Browser / Node | Transpiled to JS |