JSFiddle - React, Tailwind, and code Playground

HTML

<select class="check" name="first">
    <option value="">Select</option>
    <option value="some" required="true">Some required</option>
    <option value="other">Other Value</option>
    <option value="few" required="true">Few required</option>
</select>
<select class="check" name="second">
    <option value="">Select</option>
    <option value="some" required="true">Some required</option>
    <option value="other">Other Value</option>
    <option value="few" required="true">Few required</option>
</select>
<select class="check" name="third">
    <option value="">Select</option>
    <option value="some" required="true">Some required</option>
    <option value="other">Other Value</option>
    <option value="few" required="true">Few required</option>
</select>
<select name="other">
    <option value="">Select</option>
    <option value="some" required="true">Some required</option>
    <option value="other">Other Value</option>
    <option value="few" required="true">Few required</option>
</select>
<button class="check-select">Check!</button>

JavaScript

$(document).on('click', '.check-select', function () {
    var error = $(".check").find("option:selected").map(collectErrors);
    for (var i = 0; i < error.length; i++) {
        alert(error[i]);
    }
});

function collectErrors() {
    if ($(this).attr("required") == undefined) {
        var $parent = $(this).parent();
        return "Please select one of the folowing:" + findRequired($parent) + " For the select box " + $parent.attr("name");
    }
}

function findRequired($parent) {
    return $parent.find("option[required=true]").map(function () {
        return $(this).text();
    }).toArray().join()
}