JSFiddle - React, Tailwind, and code Playground

HTML

Follow @amazon, @facebook & @anyoneelse

JavaScript

function replaceAtMentionsWithLinks ( text ) {
    return text.replace(/@([a-z\d_]+)/ig, '<a href="http://twitter.com/$1">@$1</a>'); 
}

var replaced = replaceAtMentionsWithLinks(document.body.textContent);
document.body.innerHTML = replaced;