JSFiddle - React, Tailwind, and code Playground

HTML

<select id="myselect">
<option>a</option>
<option>b</option>
<option>c</option>
</select>
<div id="result"></div>

JavaScript

var a = $("#myselect")
$("#result")
    .append(a.width())
    .append(', ')
    .append(a.innerWidth())
    .append(', ')
    .append(a.outerWidth());