Typeahead.js doesn't have an "updater" option.
Instead you can write an event handler which will use typeahead's selected event (i.e. typeahead:selected) e.g.
var numSelectedHandler = function (eventObject, suggestionObject, suggestionDataset) {
alert(suggestionObject.num);
};
typeahead.on('typeahead:selected', numSelectedHandler);
A working example can be found here: