List of languages that compile to JS

Rules: tag all commercial projects with [commercial], try to preserve the existent taxonomy by use of tagging [tag]
Notice: try not to override other people contributions (race condition)

CoffeeScript Family (& Friends)

• CoffeeScript Unfancy JavaScript

Family (share genes with CoffeeScript)

• Coco a CoffeeScript dialect that aims to be more radical and practical, also acts as a test bed for features that get imported in CoffeeScript.
• Parsec CoffeeScript is CS based on parser combinators. The project's aim is to add static metaprogramming (i.e. macros + syntax extensibility) to Coffee Script (CS), similar to how Metalua adds such features to Lua. The resulting compiler, once merged with the official compiler, should be usable as a drop-in replacement for it.

Friends (philosophically related)

• Kaffeine Enhanced Syntax for Javascript.
• Jack Making programming playful.

JavaScript

• Closure Compiler An optimizing compiler. Can generate a (line/col)-number mappings file.

Ruby

• HotRuby runs opcode, compiled by YARV on Ruby inside a web browser or in Flash.
• rb2js converts Ruby to JavaScript.
• Red writes like Ruby and runs like JavaScript

Python

• PYXC-PJ [CS friend] Python to JS. Can generate a (line/col)-number mappings file.
• Pyjamas Python to JS.
• Skulpt Python. Client side.

Lisp, Scheme

• Parenscript subset of Common Lisp to JS.
• Sibilant Javascript with a lisp
• Moby Scheme a Scheme running in JS.
• scheme2js Scheme to JavaScript
• ClojureScript translates code written in a very small subset of Clojure.
• Scriptjure library for generating javascript from Clojure forms.

OCaml

• Ocamljs OCaml to JS

Haskell

• UHC (Utrecht Haskell Compiler) backend converts UHC core to JavaScript, allowing the compiling of Haskell code to JS.
• YHC (York Haskell Compiler) backend, as above but with YHC core language.

Multitarget

• Haxe compiles to several platforms (C++, Flash, JS, Neko, PHP).
• Clue C language compiler to different runtimes (Lua, JS, Perl 5, C, Java, CL).
• Fantom Evolutionary Object Oriented language emphasizing succinct and effective APIs (JVM, CLR, JS).

Tierless languages (produce both client & server)

• One Pot Application [free for non commercial] industrial programming language for high-security distributed web applications.
• Fun A programming language for realtime webapps - compiles to client-side and server-side JS
• Ur in the tradition of ML and Haskell.
• WebSharper lets you compile F# to JS
• mobl the new language for programming the mobile web.
• GWT Java to JS.

Others

• Oia a port of Io to Javascript
• NS Basic/App Studio [commercial] Visual Basic-style BASIC to Javascript compiler. Includes IDE. Targets iOS and Android.
• Emscripten LLVM to Javascript compiler
• Objective J shares with JavaScript the same relationship that Objective-C has with the C programming language: that of being a strict, but small, superset.
• Clamato a Smalltalk dialect that is designed to operate within the JavaScript runtime.
• Flapjax Event-driven, reactive evaluation.
• StratifiedJS JavaScript + structured concurrency.
• haXe Multiplatform language that can compile to Javascript, Flash (10, 9, 8), Neko VM, PHP, C++, and soon C# and Java. Supports type inference, optional static typing, and other nice things.

Static typed

• Script# compiles C# to JS.
• MileScript a strongly-typed language similar to C# and Java, but which compiles to JS.
• Mascara enhances JavaScript with powerful features like classes, namespaces and type-checking