Is there a way to use C++ in JavaScript?

From this, I found out that JavaScript is written in C++. I also have found out/deduced that a majority of JavaScript is C++ (e.g. Math.atan+"" and Math.atan.toString() yielding "function atan() { [native code] }"). The [native code I assume to be C++, else what would be the point of 'hiding' it?

My question is there a way to utilize C++ in JavaScript? To use it in a function or in the JavaScript platform?

Solution

The emscripten project allows you to to generate Javascript from C and C++:

Emscripten is an LLVM-to-JavaScript compiler. It takes LLVM bitcode - which can be generated from C/C++, using llvm-gcc (DragonEgg) or clang, or any other language that can be converted into LLVM - and compiles that into JavaScript, which can be run on the web (or anywhere else JavaScript can run).

and through methods like ccall and cwrap you can call C functions:

Using the example from the site, this C++ code which used extern "C" to prevent name mangling:

#include <math.h>

extern "C" {

int int_sqrt(int x) {
  return sqrt(x);
}

}

can be compiled like so:

./emcc tests/hello_function.cpp -o function.html -s EXPORTED_FUNCTIONS="['_int_sqrt']"

and used in Javascript:

int_sqrt = Module.cwrap('int_sqrt', 'number', ['number'])
int_sqrt(12)
int_sqrt(28)

embind can be used for C++ functions and classes. The quick example from the site is as follows:

// quick_example.cpp
#include <emscripten/bind.h>

using namespace emscripten;

float lerp(float a, float b, float t) {
    return (1 - t) * a + t * b;
}

EMSCRIPTEN_BINDINGS(my_module) {
    function("lerp", &lerp);
}

and compile:

emcc --bind -o quick_example.js quick_example.cpp

and use in Javascript:

<!doctype html>
<html>
  <script src="quick_example.js"></script>
  <script>
    console.log('lerp result: ' + Module.lerp(1, 2, 0.5));
  </script>
</html>