JSFiddle - React, Tailwind, and code Playground

HTML

<select size="6" name="operator[]" id="operator[]" size="5" multiple="">
    <option value="1" selected>One</option>
    <option value="2" >Two</option>
    <option value="10" >Ten</option>
</select>

JavaScript

$(function(){alert($("#operator\\[\\]").val())})