JSFiddle - React, Tailwind, and code Playground

HTML

<p>Please select your region and state:</p>
<select id="region">
    <option id="please_select">-- Select Region --</option>
    <option id="wm">West Malaysia</option>
    <option id="em">East Malaysia</option>
</select>
<select id="state"></select>
<br/>
<br/>
<button id="showResult">Show Result</button>
<br/>
<br/>
<div id="result"></div>

JavaScript

$(document).ready(function () {

    // Hide states dropdown
    $("#state,#showResult").hide();

    // Put all West Malaysia states in a variable
    var wmStates = "<option>Perlis</option><option>Kedah</option><option>Perak</option><option>Pulau Pinang</option><option>Selangor</option><option>Melaka</option><option>Negeri Sembilan</option><option>Johor</option><option>Pahang</option><option>Terengganu</option><option>Kelantan</option>";

    // Put all East Malaysia states in a variable
    var emStates = "<option>Sarawak</option><option>WP Labuan</option><option>Sabah</option>";

    // Listen to #region dropdown change
    $("#region").change(function () {

        // Get the selected value
        var selected = $(this).val();

        // Show states dropdown
        $("#state,#showResult").show();

        // If West Malaysia selected, show West Malaysia states
        if (selected == 'West Malaysia') {
            // Show dropdown set for West Malaysia
            $("#state").html(wmStates);
        }
        // If East Malaysia selected, show East Malaysia states
        else if (selected == 'East Malaysia') {
            // Show dropdown set for East Malaysia
            $("#state").html(emStates);
        }
        // If -- Region -- is selected
        else if (selected == '-- Select Region --') {
            // Hide #states, button & #result
            $("#state,#showResult,#result").hide();

            // Ask user to select a region
            alert('Please select your region');
        }
    });

    // Listen to button click
    $("#showResult").click(function () {

        // Get selected value and put in variables
        var regionSelected = $("#region").val();
        var stateSelected = $("#state").val();

        // Put the variables inside the #result div
        $("#result").html("Region: " + regionSelected + "<br/>State: " + stateSelected);
    });

});