JSFiddle - React, Tailwind, and code Playground

HTML

<select id="selectMenu">
    <option value="1">1</option>
    <option value="2">2</option>
</select>

<input id="button" name="button" type="button" value="Click Me" />

JavaScript

var initEvt = function (el, type) {
        var e = document.createEvent('MouseEvents');
        e.initEvent(type, true, true, window);
        el.dispatchEvent(e);
    },
    selMenu;

selMenu = document.getElementById('selectMenu');

document.getElementById('button').onclick = function () { 
 	initEvt(selMenu, 'mouseover');
    initEvt(selMenu, 'mousedown');
    initEvt(selMenu, 'mouseup');
    initEvt(selMenu, 'click');   
}