JavaScript runs everywhere and is familiar to a huge community of developers, and consequently many applications are written in JavaScript these days. There are times however when other languages are desired, for example because of existing codebases, preferred language features, or performance. In this talk we'll discuss writing and deploying web applications that use both handwritten JavaScript and another language like C++ that has been compiled into JavaScript. We will present the advantages of that approach, open source tools like Emscripten and Embind that enable it, asm.js optimizations which let it run at near-native speeds, and several real-world examples of such projects.