var countriesArray = $.map(countries, function (value, key) { return { value: value, data: key }; });

// Setup jQuery ajax mock:
$.mockjax({
    url: '*',
    responseTime: 2000,
    response: function (settings) {
    var query = settings.data.query,
    queryLowerCase = query.toLowerCase(),
    re = new RegExp('\\b' + $.Autocomplete.utils.escapeRegExChars(queryLowerCase), 'gi'),
    suggestions = $.grep(countriesArray, function (country) {
            // return country.value.toLowerCase().indexOf(queryLowerCase) === 0;
            return re.test(country.value);
        }),
        response = {
            query: query,
            suggestions: suggestions
        };

        this.responseText = JSON.stringify(response);
    }
});

$('#country').autocomplete({
    lookup: countriesArray,
    minChars: 1,
    onSelect: function (suggestion) {
        $('#selection-country').html('You selected: ' + suggestion.value);
    },
    showNoSuggestionNotice: true,
    noSuggestionNotice: 'Sorry, no matching results',
    groupBy: 'category'
});