One really nice thing about the level of C++11 and C++14 (and even C++1z) support in clang and libc++ is that it has let emscripten remain at the forefront of support as well. While emscripten's compiler is a bit older (clang 3.3-based), I just updated the libc++ that emscripten uses to a current version (as of 3 days ago).