Embind + Asyncify

embind-asyncify.sh

# Install tip-of-tree Emscripten
$ emsdk install tot
$ emsdk activate tot
# Build with Embind and Asyncify enabled
$ emcc --bind -s ASYNCIFY mylib.cpp -o mylib.html

mylib.cpp

#include <string>
#include <iostream>
#include <emscripten/bind.h>

using namespace std::string_literals;
using emscripten::val;

static const val fetch = val::global("fetch");

int main() {
	val response = fetch("https://httpbin.org/headers"s).await();

	if (response["ok"].as<bool>()) {
		auto text = response.call<val>("text").await().as<std::string>();
		std::cout << "Response:" << std::endl << text << std::endl;
	} else {
		std::cerr << "Error " << response["status"].as<int>() << ": "
		          << response["statusText"].as<std::string>() << std::endl;
	}

	return 0;
}