JSFiddle - React, Tailwind, and code Playground

HTML

<select id="cd-dropdown" class="cd-select">
<option value="-1" selected >Menu</option>
<option value="http://google.com" class="home">1</option>
    <option value="http://google.com" class="home">2</option>
</select>

<div class="overlay"></div>

CSS

.overlay {
    width: 100%;
    height: 100%;
    opacity: 0.7;
    background: black;
}

JavaScript

$(document).ready(function() {
    $(".overlay").hide();
    
    $("#cd-dropdown").change(function(event) {
        $("#cd-dropdown").blur();
    }).focus(function() {
        $(".overlay").fadeIn();
    }).blur(function() {
        $(".overlay").fadeOut();
    });
});