JSFiddle - React, Tailwind, and code Playground

HTML

<button id="reproButton">Click me to open the select control</button>
<br/>
<br/>
<select>
    <option>This</option>
    <option>is</option>
    <option>a</option>
    <option>select</option>
    <option>flyout.</option>
    <select>

JavaScript

window.addEventListener("load", function () {
    document.getElementById("reproButton").addEventListener("click", function () {
        var selectElement = document.getElementsByTagName("select")[0];

        var event = document.createEvent("MouseEvents");
        event.initMouseEvent("mousedown", false, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
        selectElement.dispatchEvent(event);
    });
});