It&#x27;s missing the most important React feature (Virtual-DOM diff.).<p>More specifically, he&#x27;s manually adding and keeping track of all DOM elements. Once elements need to be updated, he would need to go back in the DOM and manually add&#x2F;remove&#x2F;change elements.. welcome back to the jquery messy world. Whereas with React, the render function doesn&#x27;t change because it gets smartly rerendered.<p>Also, as far as I&#x27;m concerned, jsx is a big part of what I like about React. Basically, being able to add html from javascript instead of using all kind of hacks.