JSFiddle - React, Tailwind, and code Playground

HTML

<select id="mySelectBox"><option value="five">5</option>
<option value="6" selected="selected">six</option>
</select>

JavaScript

$('#mySelectBox option').each(function() {
    if (this.selected == true) {
       alert($(this).val() + " is selected");
    } else {
       alert($(this).val() + ' is not');
    }
});