emscripten::val - How to pass Function type as an argument?

[gerald-dotcom]

I have a JS function like this,

function foo(functionName){
  console.log(typeof functionName);

}

My emscripten code looks like this, 

int call() {

emscripten::val Global = emscripten::val::global("window");

emscripten::val FunctionName = emscripten::val::global("window")["zoo"];

emscripten::val GetType = Global.call<emscripten::val>("foo", FunctionName);

};

However, the type that emscripten pass to Function foo is an Object not a reference to function

Question maybe vague. I somehow need to pass the right type. 

I tested this in Pure JS and it can differ functions and objects easily.