function request(url) {    // this is where we're hiding the asynchronicity,    // away from the main code of our generator    // `it.next(..)` is the generator's iterator-resume    // call    makeAjaxCall( url, function(response){        it.next( response );    } );    // Note: nothing returned here!}function *main() {    var result1 = yield request( "http://some.url.1" );    var data = JSON.parse( result1 );    var result2 = yield request( "http://some.url.2?id=" + data.id );    var resp = JSON.parse( result2 );    console.log( "The value you asked for: " + resp.value );}var it = main();it.next(); // get it all started