JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" class="extension" value=".com" />
<input type="button" class="extension" value=".net" />
<input type="button" class="extension" value=".info" />
<input type="button" class="extension" value=".org" />
<br><br>
<a href="www.example.com" id="myLink" >www.example.com</a>

JavaScript

$(".extension").click(function() {
    var defaultAddress = "www.example";
    $("#myLink")[0].href = defaultAddress + this.value;
    $("#myLink")[0].innerText = defaultAddress + this.value;
});