JSFiddle - React, Tailwind, and code Playground

HTML

<select multiple>
    <option>One</option>
    <option>Two</option>
</select>

JavaScript

$(function() {
    if ($("select[multiple]").length) {
    alert("worked");
}


if ($("select").attr("multiple")) {
    alert("worked");
}


if ($("select").attr("multiple") != 'undefined') {
    alert("worked");
}

});