JavaScript would definitely be my first choice if I had to integrate another scripting language into a native program today (doubly so if the eventual target is

JavaScript would definitely be my first choice if I had to integrate another scripting language into a native program today (doubly so if the eventual target is web, like the author implies with WebAssembly support). Depending on your needs (small vs. fast, low memory usage vs. full JIT, etc.) you can pick anything from JerryScript / QuickJS all the way to V8. Perhaps the only thing missing is a universal C/C++ API for embedding JavaScript engines that lets you swap out easily to test different trade-offs.