JSFiddle - React, Tailwind, and code Playground

HTML

<div class="custom-select" style="height: 100px; width: 100px; background:red">
    <select id="operator_select">
        <option value="1">1</option>
        <option value="2">2</option>
    </select>
</div>

JavaScript

$(function () {
    function open(elem) {
        if (document.createEvent) {
            var e = document.createEvent("MouseEvents");
            e.initMouseEvent("mousedown", true, true, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
            elem[0].dispatchEvent(e);
        } else if (element.fireEvent) {
            elem[0].fireEvent("onmousedown");
        }
    }

    $(".custom-select").click(function () {
        open($(this).find('select'));
    });
});