RunJS

The JavaScript playground
for your desktop

Diamond
isAnagram
Fetch
const limit = 15;
let count = 1;
Array(limit).fill(0).reduce((acc, _, index) => {
  const spaces = ' '.repeat(
    Math.abs(limit - count) / 2
  );
Other platforms

Explore and experiment with JavaScript and TypeScript, visualise your ideas and get instant feedback as you type.

Platforms

Latest version: 2.1.3

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

Features

Exploring JavaScript has never been easier. Live feedback as you type, with per-line results makes it super clear what your code is doing.

Quirky
Web Audio
Server

In RunJS you have access to Node and Browser APIs, including full DOM access. This gives you a level of versatility that's not possible in a standard REPL or Chrome console.

Babel and TypeScript support enables you to write modern, up-to-date syntax.

TypeScript
Babel

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

Lodash
Redux

Testimonials

Since the first release of RunJS in late 2018, many people from around the world, with all kinds of backgrounds have said very kind words about it.

Awesome JS playground here. Its similar to Swift playgrounds - every line of JS code will be evaluated separately, with output printed on the right. Great tool for exploring JS!
Stephen Grider

Stephen Grider

RunJS - a desktop app that serves as a JavaScript scratchpad. This is one of my favorite tools for debugging and testing things quickly.
Joe Previte

Joe Previte

If you want to know what a piece of JS code will do, there's no substitute for just RUNning it and seeing the result! RunJS has become an essential tool in my daily JS development, writing, and teaching work, unseating a bunch of other tools like consoles, CLIs, and in-browser code editors.
Kyle Simpson

Kyle Simpson

This. is. awesome: RunJS, a JavaScript playground for Mac. Supports TypeScript, Babel transpilation, Node and browser APIs altogether, import Node modules from a folder, and more.
Flavio Copes

Flavio Copes

Was looking for a simple Javascript REPL Mac app and ran across RunJS.. this is perfect. simple little sandbox to tinker with JS before writing it for real in my main environment.
Paul Stamatiou

Paul Stamatiou

If you want to quickly see what a wee JavaScript snippet evaluates to, RunJS is a delightful way to find out. It's free. And pretty. And cross-platform. I dig it.
Michael Uloth

Michael Uloth

So grateful to have discovered RunJS. It's so much easier to practice JavaScript when you can see the solution in real time!
Cassandra Rossall

Cassandra Rossall