// jQuery used
var SearchableTextEnteredEvent = Rx.Observable.fromEvent(WikipediaSearch, "keyup")
  .select(function (eventData) {
    return $(eventData.target).val();
  })
  .where(function (text) {
    return text.length >= 4;
  });

var SearchableTextLogger = Rx.Observer.create(
  function (text) {
    log(WikipediaSearch_Log, text);
  }, function (error) {
    window.alert("Unexpected error occured: " + error);
  },
  undefined
);

SearchableTextEnteredEvent.subscribe(SearchableTextLogger);