JSFiddle - React, Tailwind, and code Playground

HTML

<select id="comboA">
    <option value="">Select combo</option>
    <option value="Value1">Text1</option>
    <option value="Value2">Text2</option>
    <option value="Value3">Text3</option>
</select>
To test, change the value

JavaScript

document.getElementById('comboA').addEventListener('change', getSelection, false);

function getSelection() {
    var value = this.options[this.selectedIndex].value;
    alert(value);
}