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Online TypeScript Compiler and Playground

Browser-based compiler and playground for TypeScript — Progsity IDE.

About TypeScript

TypeScript adds static types to JavaScript—catching mistakes before runtime and scaling teams with interfaces, generics, and tooling integration. This TypeScript playground compiles and runs your .ts snippets so you can practice types without a local tsc watch process.

Use it for algorithm katas with explicit types, or to compare structural typing vs nominal patterns. The compile output tab surfaces type errors distinctly from runtime failures.

Ideal for interview prep and teaching: share a link after sign-in so reviewers see the exact code you ran.

How to use

  1. Annotate variables and function return types. Start from the default snippet that logs a typed string.
  2. If compilation fails, read the error—often a missing type guard or wrong generic argument.
  3. Run after types pass; runtime errors still appear in stderr.

FAQ

Is TypeScript free to run here?›

Yes. Compilation and execution are free; saved snippets follow account limits.

Strict mode?›

The sandbox uses a practical TS config similar to typical Node projects. If something is rejected, simplify types or add assertions cautiously.

Can I save .ts files?›

Yes when signed in; they appear in My Snippets.

Why compile errors?›

TypeScript stops invalid programs before run. Fix the first error, then recompile.

Playground vs IDE?›

Single-file playground—great for learning—not a full project with tsconfig paths.

Related languages

Code examples

Tap “Try this” to load sample code into the editor above.

  • Generic identity

    function id<T>(x: T): T {
  return x;
}
console.log(id(42));

  • Interface + object

    type User = { name: string; id: number };
const u: User = { name: "Ada", id: 1 };
console.log(`${u.name} #${u.id}`);

  • Union narrowing

    function fmt(x: string | number): string {
  if (typeof x === "number") return x.toFixed(2);
  return x.toUpperCase();
}
console.log(fmt(3.1415));
console.log(fmt("hello"));

  • Readonly array

    const xs: readonly number[] = [1, 2, 3];
const sum = xs.reduce((a, b) => a + b, 0);
console.log(sum);