Why TypeScript Matters for Hiring
TypeScript isn't just a "nice to have" anymore—it's table stakes for professional development. Here's why it should be on your requirements list:
The Business Case
Fewer bugs in production: Microsoft found that TypeScript catches 15% of bugs at compile time that would otherwise reach users. For a company like Stripe processing billions in payments, that's the difference between trust and catastrophe.
Faster onboarding: New developers can understand codebases faster because types serve as documentation. Airbnb reported 30% faster ramp-up time for new engineers after migrating to TypeScript.
Better collaboration: In large teams (50+ engineers), TypeScript's type system prevents the "I changed this, why did that break?" problem. Slack cited this as a primary reason for their TypeScript adoption.
What TypeScript Developers Build
Frontend Applications
TypeScript is the standard for React, Vue, and Angular projects:
- Stripe Dashboard: Complex financial data visualization with type-safe API responses
- Figma: Real-time collaborative design with typed state management
- VS Code: Microsoft's editor is 100% TypeScript (and it edits TypeScript too)
Backend Services
Node.js + TypeScript is increasingly common:
- Slack: Their desktop app backend uses TypeScript
- Notion: Type-safe API routes and database queries
- Linear: The project management tool runs TypeScript end-to-end
Full-Stack Applications
The same language everywhere:
- Next.js applications: Type-safe from API routes to React components
- tRPC and GraphQL: End-to-end type safety between frontend and backend
- Prisma ORM: Type-safe database queries
Skills to Look For
Must Understand (Not Just Use)
1. Type Inference vs. Explicit Types
A junior developer annotates everything:
const name: string = "hello"; // Redundant
A senior developer lets TypeScript infer:
const name = "hello"; // TypeScript knows it's a string
2. Union Types and Narrowing
This is where TypeScript shines. Ask candidates to explain:
function processValue(value: string | number) {
if (typeof value === "string") {
// TypeScript knows it's a string here
}
}
3. Generics
The difference between mid-level and senior. Generics make code reusable:
function getFirst<T>(arr: T[]): T | undefined {
return arr[0];
}
Red Flags
- Uses
anyeverywhere (defeats the purpose of TypeScript) - Can't explain the difference between
interfaceandtype - Turns off strict mode because "it's annoying"
- Only knows TypeScript in the context of one framework
Interview Questions That Reveal Skill
For Any Level
Q: "Why would a company migrate from JavaScript to TypeScript?"
- Junior answer: "TypeScript catches errors"
- Senior answer: Discusses specific bug categories, IDE benefits, documentation value, and migration tradeoffs
For Mid-Level
Q: "How do you type a function that can accept any object with an 'id' field?"
Look for: Generic constraints, understanding of structural typing
For Senior
Q: "Explain conditional types and give a real-world use case"
Look for: Template literal types, mapped types, and practical examples like type-safe API responses
Recruiter's Cheat Sheet
Resume Signals
✅ Look for:
- Mentions TypeScript in production contexts, not just tutorials
- Experience with strict mode enabled
- Contributions to TypeScript ecosystem (DefinitelyTyped, libraries)
🚫 Be skeptical of:
- "TypeScript expert" with only 6 months experience
- No mention of type safety in project descriptions
- Only used TypeScript because the project started with it
GitHub Red Flags
anytypes scattered throughout code// @ts-ignorecomments everywhere- tsconfig.json with strict mode disabled
- No type declarations in function parameters
Common Hiring Mistakes
1. Treating TypeScript as Separate from JavaScript
TypeScript IS JavaScript with types. A candidate who's excellent at JavaScript but hasn't used TypeScript will be productive in days. The reverse isn't true—someone who learned TypeScript without understanding JavaScript fundamentals will struggle.
2. Overvaluing Advanced Type Gymnastics
Complex type manipulations impress in interviews but rarely matter in production code. Focus on whether candidates write maintainable, well-typed code, not whether they can implement a recursive conditional type.
3. Ignoring the Migration Story
Most codebases aren't pure TypeScript. Ask about experience migrating JavaScript to TypeScript, working with untyped libraries, and gradual adoption strategies.
4. Not Testing TypeScript Configuration
Ask candidates about tsconfig.json settings. Developers who work with strict mode enabled write better code than those who turn it off. Understanding compiler options reveals production experience.