RunJS LogoRunJS

The TypeScript Playground for Rapid Prototyping

class Greeter<T> {
greeting: T;
constructor(message: T) {
this.greeting = message;
greet() {
return this.greeting;

Other platforms

Explore TypeScript, run code with instant results, see type information, install NPM packages and much more.


Latest version: 2.7.3

macOS (.app)Universal
Windows (.exe)64 bit
Linux (.deb)64 bitARMARM 64
Linux (.tar.gz)64 bitARMARM 64

Made for TypeScript tinkerers

RunJS makes it easy to try out new ideas before implementing them into your project.

I wish I had RunJS when I was a student [at] FlatironSchool. Awesome way to learn JavaScript and TypeScript fundamentals. Also perfect for exploring new libraries.



With access to both Node and Browser APIs, RunJS is a very versatile environment to tinker in.

RunJS is a fantastic tool for prototyping and testing JavaScript and TypeScript code.
Mathew Layton

Mathew Layton

NPM integration makes trying out new libraries quick and easy.Premium

Just discovered RunJS and it's a game changer! Much better than opening VSCode, creating a test.js file and running 'node test.js'. 😅
Maxim Orlov

Maxim Orlov

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Go on, give it a try.