JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/selectize.js/0.12.4/js/standalone/selectize.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/selectize.js/0.12.4/css/selectize.min.css">
<select class="form-control pickerSelectClass" id="countries"></select>
<button type="button" onclick="addFiji();">Add "Fiji"</button>

JavaScript

function addFiji(){
  var $select = $('#countries').selectize();
  var selectize = $select[0].selectize;
  selectize.addOption({"name":"Fiji"});
  selectize.addItem('Fiji');
  selectize.refreshOptions();
}

var countries = [{"name":""}, {"name":"Afghanistan"}, {"name":"Belgium"}, {"name":"China"},{"name":"Denmark"}, {"name":"Estonia"}, {"name":"Finland"}, {"name":"Greece"}];

$.ajax({
  url: '/echo/json/',
  type: 'POST',
  dataType: 'json',
  data: { json: JSON.stringify(countries) },
  error: function(err) { console.log(err); },
  success: function(options) {
    $('#countries').selectize({
    valueField: 'name',
    labelField: 'name',
    searchField: 'name',
    maxItems: 3,
    preload: true,
    options: options,
    create: false,
    });
	} 
});