JSFiddle - React, Tailwind, and code Playground

HTML

<label for="marketplaces">Marketplaces:</label>
    <select class="select2" multiple id="marketplaces">
        <option value="DE">Germany</option>
        <option value="UK">United Kingdom</option>
        <option value="FR">France</option>
        <option value="ES">Spain</option>
        <option value="IT">Italy</option>
        <option value="US">United States</option>
</select>
<button id="clicker">click</button>

JavaScript

$('#clicker').click(function(){
var multiselect = $('#marketplaces').val();
alert(multiselect);
});