Emscripten Alternatives
Emscripten is described as 'LLVM to JavaScript compiler. It takes LLVM bitcode (which can be generated from C/C++ using Clang, or any other language that can be converted into LLVM bitcode) and compiles that into JavaScript, which can be run on the web (or anywhere else JavaScript can run)' and is an app. There are three alternatives to Emscripten for Linux, Mac and Windows. The best alternative is Cheerp. It's not free, so if you're looking for a free alternative, you could try Clue (compiler) or CrossBridge.
Cheerp compiles C++ into modern WebAssembly and JavaScript. With Cheerp, you can write a new web application, or port an existing one, in C/C++. Cheerp will then generate WebAssembly/JavaScript code that can run on any browser and device.
Cheerp vs Emscripten opinions
It compiles the LLVM output of a C++ compiler to JavaScript, just like Emscripten.
0Clue is an experimental C compiler that generates code for high-level dynamic languages such as Lua, Javascript, Perl5 and Common Lisp, as well as non-dynamic languages like C and Java. It supports the complete ANSI standard, including pointer arithmetic
This app doesn't have any features at the moment.
CrossBridge is the open-source version of Adobe FlasCC (formerly the Alchemy project).
This app doesn't have any features at the moment.