The new fbml version which is 1.1 has included an Ajax Typeahead object as a FBML tag. So it is not necessary to create our own javascript to implement the typeahead object. You can implement the feature using a code like this
1: <fb:fbml version="1.1">2:Service Provider :<fb:typeahead-input name="serviceProvider" autocomplete="off" >
3: <fb:typeahead-option value="mob" >Mobitel</fb:typeahead-option>
4: <fb:typeahead-option value="dia" >Dialog</fb:typeahead-option>
5: <fb:typeahead-option value="tig" >Tigo</fb:typeahead-option>
6: <fb:typeahead-option value="hut" >Hutch</fb:typeahead-option>
7: </fb:typeahead-input>
8: </fb:fbml>
After adding above code, the resulting input element will be like this
