-pseudo code- function wait.for ( asyncFn, params ) { //call the async fn, returns immediately asyncFn(params, function(err,data){ //

-pseudo code- function wait.for ( asyncFn, params ) { //call the async fn, returns immediately asyncFn(params, function(err,data){ //here the data is ready thisFiber.err = err; thisFiber.data = data; thisFiber.resume(); //resume execution (after yield()) }); //we're in a fiber, so we can yield() to node's event loop thisFiber.yield(); //pause here, give back control to node's event loop // the next line will be executed when thisFiber.resume() is called if (thisFiber.err) throw thisFiber.err; // throw into the caller of wait.for return thisFiber.data; //ok }