main.rs

extern crate libc;
extern "C" {
    fn emscripten_asm_const_int(script: *const libc::c_char, ...) -> libc::c_int;
}

macro_rules! c_str {
    ($s:expr) => {
        concat!($s, "\0").as_ptr() as *const _
    }
}

macro_rules! js {
    (($($name:ident = $expr:expr),*) {$($tt:tt)*}) => {
        unsafe { emscripten_asm_const_int(c_str!(concat!(
            $(
                "var ", stringify!($name), " = $0; ",
            )*
             stringify!($($tt)*))), $($expr),*) }
    };
}

macro_rules! js_raw {
    (($($name:ident = $expr:expr),*) {$code:expr}) => {
        unsafe { emscripten_asm_const_int(c_str!(concat!(
            $(
                "var ", stringify!($name), " = $0; ",
            )*
             $code)), $($expr),*) }
    };
}

fn main() {
    println!("Hello world 2");
    println!("test: {}", js!{(){
        var testing = 55;
        function test(i) { return i; }
        return test(testing)
    }});
    println!("test2: {}", js!{(arg0 = 78){
        var testing = 55;
        return testing * arg0;
    }});
    let test = "hello".as_ptr();
    js!{(v = test){
        console.log(Pointer_stringify(v, 5));
    }};
    js_raw!{(){r#"console.log('Hello world 2');"#}};
}