JSFiddle - React, Tailwind, and code Playground

HTML

<div id='testdiv'>
    <div class='myclass'>
        [First Title|<a class="external" href="http://test.com">http://test.com</a>]
        Another line
        [Second Title|<a class="external" href="http://test.com">http://test.com</a>]
        More text
        [Third Title|<a class="external" href="http://test.com">http://test.com</a>]
    </div>
</div>

JavaScript

var textContainer = document.getElementById("testdiv");
var linkText = textContainer.innerHTML;
var pattern = /\[([^|]+)\|([^>]+.?)[^<]*(<\/a>)\]/g;
var result = linkText.replace(pattern, "$2$1$3");

textContainer.innerHTML = result;