Web-based REPL's for many languages

I only just recently learned the term “REPL”. It essentially means “command line”. You type code in, it runs, you see output.

Read, Eval, Print, Loop.

JavaScript

We’re web folks ’round here, so JavaScript makes for an easy example. The “console” in your browser’s DevTools is a REPL for JavaScript.

There is a console on CodePen as well, which can be useful because you can create examples that link to REPL output:

You could also think of CodePen as a REPL for HTML, CSS, and JavaScript, alongside a variety of preprocessor languages like Sass, Less, Stylus, CoffeeScript, etc.

Future JavaScript

Babel is a compiler that turns future-syntax JavaScript into current-generation JavaScript. You can play with Babel right on their website, and they straight up call it a REPL:

CoffeeScript offers their own as well:

Ruby

repl.it is a a web-based REPL for a bunch of languages, including Ruby.

You can save your examples for later reference as well.

Python

Skulpt lets you run Python entirely in the browser.

PythonAnywhere also has IPython, an online interpreter.

PHP

repl.it seems to be a good choice here again:

For the record, repl.it supports an impressive number of languages, so if you’re looking for a specific one, you might try there first.

Java

Java REPL has a console that is as simple as it gets:

Swift

IBM makes a REPL for Swift. They call it a sandbox, which is a common name for these kinds of things.

Clojure

Clojure is weird. I enjoyed TryClojure because it not only allows you to write/execute Clojure, but also walks you through learning it interactively:

Happy coding!