JSFiddle - React, Tailwind, and code Playground

HTML

<label for="in">Enter something:</label>
<input type="text" id="in">

JavaScript

$(function() {
    var data1 = 'abcdefghijklmnopqrstuvwxyz'.split('');
    var data2 = 'cat dog fish shark unicorn sasquatch flamingo dingo snake mouse rat'.split(/\s+/g);
    
    $('#in').autocomplete({
        minLength: 0, // so it shows straight away without typing anything
        source: function (request, response) {
            if ((request.term || '').length <= 1)
               response(filter(data1, request.term));
            else
               response(filter(data2, request.term));
        }
    }).on('focus', function () {
        $(this).autocomplete('search', '');
    });
    
    function filter(array, searchTerm) {
        var matchingItems = [];
        for (var i = 0; i < array.length; i++) {
            if (array[i].indexOf(searchTerm.toLocaleLowerCase()) >= 0)
                matchingItems.push(array[i]);
        }
        if (matchingItems.length === 0)
            return ['No Matches'];
        return matchingItems;
    }
        
});