For any codebase that more than one person will maintain for more than a few months, use TypeScript: it catches whole classes of bugs before runtime, makes refactoring safe and gives editors and AI coding tools far better context. Plain JavaScript still makes sense for short scripts, single-page browser snippets, quick prototypes and libraries where a JSDoc-typed JavaScript source is a deliberate choice. Since TypeScript compiles to JavaScript and runs the same way, this is a decision about developer workflow, not runtime performance.
Three shifts made TypeScript the default rather than an add-on.
JavaScript itself keeps improving through yearly ECMAScript releases, and the 2026 Stack Overflow Developer Survey still shows JavaScript as the most used language at 62%, with TypeScript at 43.8%. Every TypeScript developer is also a JavaScript developer, so those numbers overlap rather than compete.
TypeScript has no runtime cost. Types are erased; the JavaScript that runs is what you would have written by hand. Two caveats are worth knowing:
Runtime performance problems in either language come from the same places: unnecessary re-renders, oversized bundles, blocking the event loop, N+1 network calls. Types do not fix those, but they make the code easier to change when you fix them.
Nearly every major framework now scaffolds with TypeScript by default: Next.js, Remix and React Router, Angular, Vue, SvelteKit, NestJS, Astro. Most npm packages ship their own type definitions, and DefinitelyTyped covers many of the rest. Tools like Zod, Valibot and tRPC use TypeScript's type system to share validated types between frontend and backend, which removes a whole class of API contract bugs.
JavaScript-only codebases can get much of the editor benefit with JSDoc annotations checked by the TypeScript compiler (checkJs). Some library authors prefer this so their published source is exactly what runs, while still giving users types. It is a valid choice for a library, and rarely the right one for an application team.
For React-specific framework choices, see React vs Angular; for cross-platform mobile, Flutter vs React Native.
Coding assistants and agents work better with typed code. Type signatures tell a model what a function accepts and returns, the compiler gives an agent immediate feedback when its change breaks a contract, and type errors are cheap tests the agent can run after each edit. In practice, strict TypeScript plus good tests is one of the cheapest guardrails you can put around agent-written code, because many bad edits fail to compile before anyone reviews them. In plain JavaScript, more of those mistakes surface only at runtime.
Almost every senior frontend and Node.js engineer in 2026 writes TypeScript, so choosing it does not shrink your hiring pool. The difference between levels is depth: junior developers use types the framework gives them; senior engineers design types for shared libraries, use generics and discriminated unions well, keep strict mode on and know when to stop adding type-level cleverness. Screen with our TypeScript interview questions and JavaScript interview questions, and see pay bands on our TypeScript developer rates and JavaScript developer rates pages.
Both are free. TypeScript adds some up-front cost: configuring tsconfig, writing types for internal APIs and training engineers on stricter patterns. It pays back through fewer production bugs, faster onboarding and safer refactors. The longer a codebase lives and the more people touch it, the larger the return. For a throwaway prototype, the up-front cost may not be worth it.
Ryz Labs engineers work on your team on US business hours, in your repos and standups, with same-day code review. Only the top 1% of the tens of thousands of engineers we interview make it. You can hire TypeScript developers, JavaScript developers or full-stack developers, or bring in a dedicated team through our web application development services to migrate a JavaScript codebase to strict TypeScript while shipping features.
Typical cost is $7,000 to $15,000 per engineer per month by seniority, and you get a plan, a price and the names of the people before you start. If you only need a few hours of help converting one file, a freelance marketplace is the better fit.
For applications maintained by teams, yes in most cases: static types catch bugs earlier, make refactoring safer and improve editor and AI tooling. For short scripts and prototypes, plain JavaScript is often faster to write. TypeScript compiles to JavaScript, so runtime behavior and performance are the same.
No. Types are erased before execution, so the code runs at the same speed as equivalent JavaScript. TypeScript improves development speed and correctness, not runtime speed.
Yes, for most code. Node.js type stripping is on by default since v23.6 and v22.18 and stable since v24.12. It removes type annotations at load time but does not type check, and it does not support syntax that emits code, such as enums, without extra flags.
TypeScript 7, released in July 2026, is a native port of the TypeScript compiler written in Go. Microsoft says it is often about 10 times faster than TypeScript 6.0, which makes type checking on large codebases much quicker.
It depends on size, test coverage and how strict you want to be. Most teams migrate incrementally while shipping features, converting shared types and boundaries first. Cost is team size times duration times monthly rate, so scope the codebase before committing to a timeline.
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