JSFiddle - React, Tailwind, and code Playground

HTML

<select name="acabados[]">
<option value="1">ABC</option>
<option value="2">DEF</option>
<option value="3">GHI</option>
</select>

<select name="acabados[]">
<option value="1">ABC</option>
<option value="2">DEF</option>
<option value="3">GHI</option>
</select>

<div id="output"></div>

JavaScript

$(function () {
    var $select = $('[name="acabados[]"]');
    $select.on('change', function () {
        var output = 0;
        for (var i = 0, len = $select.length; i < len; i++) {
            output += parseInt($select.eq(i).val());
        }
        $('#output').text('Added Together = ' + output);
    }).eq(0).trigger('change');
});