callback in response node.js
//you can only return a value from an async function by passing in a callback function like so:
function longRunningFunction(param1, callback){
setTimeout(function(){
var results="O High there!";
callback(results);
}, 2000);
}
//then call the async function and pass the callback function like so
longRunningFunction("morning", function(result){
alert(result);
});