JSFiddle - React, Tailwind, and code Playground

HTML

<select id="Country"></select>
<select id="State"></select>

JavaScript

var Country = ['NEPAL', 'USA', 'CHINA'];
var NepalState = ['Gandaki', 'Bagmati'];
var USAState = ['Texas', 'California'];
var ChinaState = ['Phing', 'xing'];
$('#Country').change(function() {
    var stateOption=''; 
    var countryvar = $('#Country option:selected').val();
    switch (countryvar) {
    case 'NEPAL':
        $.each(NepalState, function(index, value) {
            stateOption += '<option>' + value + '</option>';
        });
        break;
    case 'USA':
        $.each(USAState, function(index, value) {
            stateOption += '<option>' + value + '</option>';
        });
        break;
    case 'CHINA':
        $.each(ChinaState, function(index, value) {
            stateOption += '<option>' + value + '</option>';
        });
        break;
    }
    $('#State').html('');
    $('#State').append(stateOption);
});
var CountryOption='';
$.each(Country, function(index, value) {
    CountryOption += '<option>' + value + '</option>';

});
$('#Country').append(CountryOption); 
$('#Country').trigger('change');