Handle selected event in twitter bootstrap Typeahead?

$('.typeahead').on('typeahead:selected', function(evt, item) {
    // do what you want with the item here
})

$('.typeahead').typeahead({
    updater: function(item) {
        // do what you want with the item here
        return item;
    }
})

For an explanation of the way typeahead works for what you want to do here, taking the following code example:

HTML input field:

<input type="text" id="my-input-field" value="" />

JavaScript code block:

$('#my-input-field').typeahead({
    source: function (query, process) {
        return $.get('json-page.json', { query: query }, function (data) {
            return process(data.options);
        });
    },
    updater: function(item) {
        myOwnFunction(item);
        var $fld = $('#my-input-field');
        return item;
    }
})

Explanation:

1. Your input field is set as a typeahead field with the first line: $('#my-input-field').typeahead(
2. When text is entered, it fires the source: option to fetch the JSON list and display it to the user.
3. If a user clicks an item (or selects it with the cursor keys and enter), it then runs the updater: option. Note that it hasn't yet updated the text field with the selected value.
4. You can grab the selected item using the item variable and do what you want with it, e.g. myOwnFunction(item).
5. I've included an example of creating a reference to the input field itself $fld, in case you want to do something with it. Note that you can't reference the field using $(this).
6. You must then include the line return item; within the updater: option so the input field is actually updated with the item variable.