JSFiddle - React, Tailwind, and code Playground

HTML

<textarea>
    <a href='www.google.com'></a>
</textarea>
<button id="btn">change</button>

JavaScript

var new_url = "www.stackoverflow.com";
$("#btn").click(function(){
    var text = $('textarea').html();
    $('textarea').html(text.replace(/(&lt;a [^&]*href=['"])[^'"]*(['"][^&]*&gt;)/, "\$1"+new_url+"\$2"));
});