Passing JS function to Emscripten-generated code

Question

I have a piece of C++ code converted to JavaScript via Emscripten. I would like the converted C++ code to call back to the JavaScript code that calls it. Something like:

Answer 1

I needed to write something very similar to what is described in the question. My code ended up looking like this:

C:

void call(void (*back)(char*)){
    back("Hello!");
}

JS:

function back(text){
    alert(Pointer_stringify(text));
}
var pointer = Runtime.addFunction(back);
var call = Module.cwrap('call', 'void', ['pointer']);
call(pointer);
Runtime.removeFunction(pointer);

Note that the pointer returned to the callback has to be dereferenced with Pointer_stringify.

You can find example code like this on GitHub.