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 type="button" onclick="fun()" value="click here">

JavaScript

function fun(){
    var cmb = document.getElementById('cardtype');
    var sel = cmb.options[cmb.selectedIndex].text;
        if (sel == "--- Please select ---") {
            alert('Please select a different option');
            //$('.showotherpDescription').show();
        } else {

        } 
 }