JSFiddle - React, Tailwind, and code Playground

HTML

<label class="paylabel" for="cardtype">Card Type:</label>
<select id="cardtype" name="cards">
<option value="selectcard">Please select</option>
<option value="mastercard">Mastercard</option>
<option value="maestro">Maestro</option>
<option value="solo">Solo (UK only)</option>
<option value="visaelectron">Visa Electron</option>
<option value="visadebit">Visa Debit</option>
</select>

<input id="subbutton" type="button" value="click here">

JavaScript

$(function () {
    $('#subbutton').click(function () {
        if ($('#cardtype option:selected').text() === "Please select")
        {
            alert("PLEASE SELECT");
        }
    });
});