How to take those country names where selected and when I change it changed in real time?

Question

JavaScript

<select id="countries" multiple="multiple">
    <option value="1" selected>Russia</option>
    <option value="2">USA</option>
    <option value="3" selected>Canada</option>
    <option value="4">Germany</option>
    <option value="5">Georgia</option>
</select>