JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container-fluid">
    <select class="dropDown" id="column_1">
        <option value="" selected="" disabled="">Please select</option>
        <option value="1">A</option>
        <option value="2">B</option>
        <option value="3">C</option>
        <option value="4">D</option>
    </select>
    <select class="dropDown" id="column_2">
        <option value="" selected="" disabled="">Please select</option>
        <option value="1">A</option>
        <option value="2">B</option>
        <option value="3">C</option>
        <option value="4">D</option>
    </select>
</div>
<div id="resultado"></div>

JavaScript

$("div.container-fluid").on("change", "select.dropDown", function () {
    var selectedValues = $('select.dropDown').filter(function () {
        return this.value;
    }).map(function () {
        return this.value;
    }).get();
    $('#resultado').html(JSON.stringify(selectedValues));
});