JSFiddle - React, Tailwind, and code Playground

HTML

<select id="dropdown">
    <option value="a">A</option>
    <option value="b">B</option>
</select>

JavaScript

$('#dropdown').on('change', function() {
    console.log('before', $('#dropdown').val());
    $('#dropdown').val('a');
    console.log('after', $('#dropdown').val());
});