Leporello.js

Leporello.js is an interactive functional programming environment for JavaScript.

• Interactive: Your code is executed instantly as you type, with the results displayed next to it. No need to set breakpoints for debugging. Just move the cursor to any line and see what's happening.
• Designed for functional programming: Supercharge your functional code with unprecedented developer tooling.
• Next level debugging capabilities: Visualise and navigate a dynamic call graph of your program in a time-travel manner.
• Develop HTML5 apps interactively: Modify your code and instantly see the updated version without losing the application state. Interact with your app and debug it later, similar to using a time machine.
• Save time when working on IO-heavy programs: IO operations are traced and transparently replayed on subsequent program executions.
• Self-hosted: Leporello.js source code is developed within Leporello.js itself