RunJS

RunJS is an open-source desktop app that provides a local environment for testing JavaScript and TypeScript. It functions as a playground where code executes automatically to provide immediate feedback on the results. The application is available as a desktop install for macOS, Windows, and Linux, allowing developers to run scripts outside of a web browser.

This tool is designed for developers who need an isolated space to run code experiments without the overhead of setting up a full project structure or configuring a build pipeline. It is frequently used for learning and teaching programming concepts by allowing users to see the output of their scripts in real time. By removing the need for manual compilation or terminal commands, it streamlines the process of verifying small logic blocks.

Key features

• Automatic code execution with instant results
• Support for both JavaScript and TypeScript
• Integrated code completion and type checking
• Documentation access via hover
• Ability to install NPM packages
• Local snippet saving and library management
• Access to Node.js APIs
• Access to Browser APIs

Built with Electron, the application bridges the gap between a full integrated development environment and a simple text editor. It allows users to import external dependencies from the NPM registry to test libraries locally within the playground. This architecture ensures that the environment remains separate from the main system while still providing the necessary tools for modern web development. The inclusion of both Node.js and Browser APIs means users can test code that is intended for either server side or client side execution without switching tools.

Because it supports snippet libraries, the software allows users to archive frequently used code patterns for future reference. This makes it a practical utility for developers who maintain a collection of helper functions or common API request patterns. The interface focuses on a minimal layout to keep the attention on the code and the resulting output.

RunJS serves as a lightweight utility for rapid JavaScript prototyping and educational demonstrations.