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.
LiveScript is a fork of Coco that is much more compatible with CoffeeScript, more functional, and with more features.
IcedCoffeeScript A CoffeeScript dialect that adds support for await and defer keywords which simplify async control flow.
Parsec CoffeeScript 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.
Contracts.coffee A dialect of CoffeeScript that adds built-in support for contracts.
Uberscript, a CoffeeScript fork that adds type annotations which are compiled to Google closure compiler type annotation comments.
ToffeeScript A dialect of CoffeeScript that support Asynchronous Syntax and Regexp operator =~
Caffeine A dialect of CoffeeScript that support packages and classes import, useful for browser applications
heap.coffee A dialect of CoffeeScript that offers a C-like type system with manual memory management
pogoscript language that emphasises readability, handles async control flow nicely, is friendly to domain specific languages and compiles to regular JavaScript
LispyScript A JavaScript with Lispy syntax and Macros.
Wisp Wisp is a homoiconic JavaScript dialect with clojure syntax, s-expressions and macros.
Hot Cocoa Lisp A Lisp-like language that compiles to JavaScript.
Ham looks very similar to Javascript at first, but offers (hopefully) many useful features
GorillaScript Compile-to-JavaScript language designed to empower the user while attempting to prevent some common errors, offers Macros and optional Typing
NarrativeJS JavaScript extension with asynchronous futures and promises.
jwacs JavaScript With Advanced Continuation Support.
Wind.js Wind.js is an advanced library which enable us to control flow with plain JavaScript for asynchronous programming (and more) without additional pre-compiling steps.
Continuation.js A lightweight JIT compiler for simplifying asynchronous JavaScript programming with no runtime dependences. It supports both Node.js and browser-side JavaScript and is compatible with CoffeeScript (also TypeScript, and any other scripts compile to js).
Kal makes asynchronous programming easy and clean by allowing functions to pause and wait for I/O, replacing an awkward callback syntax with a clean, simple syntax
JSPipe provides JavaScript primitives to write async code without callbacks or chained functions. Inspired by Goroutines and Channels found in Go and in Clojure. For Web and NodeJS. ES5 and ES6.
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.
Mochiscript Object-oriented JavaScript with syntactic sugar. Released as a Ruby gem.
Six Six is a language super-set of JavaScript that enables new syntactic features from the 6th edition of ECMAScript to be used, through a transpiler, in your scripts today.
jmacro Quasi-Quoted JS that you can insert Haskell values into (there is also shakespeare-js for that purpose), but also supports a more haskellish syntactic version of javascript.
Smart Mobile Studio [commercial] Object Pascal to JavaScript compiler and Delphi like IDE that brings classes, inheritance, interfaces and more to JavaScript
Elevate Web Builder [commercial] Visual development tool for web applications that compiles standard Object Pascal source code into JavaScript
Go
Go2js Line-to-line translator from Go to JavaScript.
TARDISgo Compile Golang to Haxe (then on to JavaScript, Flash, Java, C++, C#, PHP & Neko)
Multitarget
Haxe compiles to several platforms (C++, Flash, JS, Neko, PHP).
Fantom Evolutionary object-oriented language emphasizing succinct and effective APIs (JVM, CLR, JS).
LZX (Laszlo XML) LZX is OpenLaszlo's declarative user interface language, which is compiled into JavaScript 2 as an intermediary format, and further compiled into either JavaScript 1.5 or ActionScript 3.
Clue and jsc above target multiple runtimes in addition to javascript
Illumination [Commercial] Visual, cross-platform tool creates apps for Android, iPhone, iPad, Desktops and HTML5 or Flash websites. The I language underlies the tool.
js.js A JavaScript JavaScript interpreter. Instead of trying to create an interpreter from scratch, SpiderMonkey is compiled into LLVM and then emscripten translates the output into JavaScript.
Javascript Optimizers
Closure Compiler An optimizing compiler. Can generate a (line/col)-number mappings file.