function fetchData(callback) {   // get me data   callback(data);}

fetchData(function(data) {   // do something with the data});

<input type="button" id="submitButton" value="Submit" />

jQuery('#submitButton').click(function() {
     // do some funky stuff});

interface IEnumerable<T> {    IEnumerator<T> GetEnumerator();}
interface IEnumerator<T> {    bool MoveNext();    T GetCurrent();}

function fetchData() {    var products = getProducts();    for(var index = 0; index < products.size(); index++) {         // populate data          // data 1         // data 2         // data 3         // stuck    }}

interface IObservable<T> {   void Subscribe(IObserver<T> observer);}

interface IObserver<T> {    void OnNext(T value);    void OnError();    void OnCompleted();}

> X = 10;10> Y = 10;10> A = X + Y;20> X = 20;> A20

X = 22

Y = 33

A = X+Y =

function setA(){  // A=X+Y as integers
  var A = parseInt($('#X').text()) + parseInt($('#Y').text());
  $('#A').text( A );
}

setA();
$('#X,#Y').css('cursor','pointer').click(function(){
  // by reaction to a click: updates A and X or Y
  var obj = $(this);
  obj.text(parseInt(obj.text())+1);
  setA();
});