countries.html

<div class="example-countries">
  <input class="typeahead" type="text" placeholder="countries">
</div>

countries.js

var countries = new Bloodhound({
  datumTokenizer: function(d) { return Bloodhound.tokenizers.whitespace(d.name); },
  queryTokenizer: Bloodhound.tokenizers.whitespace,
  limit: 10,
  prefetch: {
    url: '../data/countries.json',
    filter: function(list) {
      return $.map(list, function(country) { return { name: country }; });
    }
  }
});

countries.initialize();

$('.example-countries .typeahead').typeahead(null, {
  name: 'countries',
  displayKey: 'name',
  source: countries.ttAdapter()
});