JSFiddle - React, Tailwind, and code Playground

HTML

<select id="drop">
    <option value="0">Please select</option>
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
</select>
<button id="add">Add to cart</button>

JavaScript

$(document).ready(function() {
    var $drop = $("#drop");
    $("#add").on("click", function() {
        if($drop.val() == 0) {
            $drop.val(1);
        }
    });
});