JSFiddle - React, Tailwind, and code Playground

HTML

<span class="widget widget-cms-link">
    <a href="/size-guide" title="Size Guide">
        <span>Size Guide</span>
    </a>
</span>

JavaScript

$$('.widget.widget-cms-link').each(function(el) {
    el.down('a').replace(new Element('button', {
        'class' : 'widget-button'        
    }).observe('click', function() {
        alert('you clicked on me');
    }).update('Your New Button'));
});