Yes, calling ReactDOM.render() hundreds of times on the same page can definitely lead to performance issues. The main concerns are startup time, interaction speed, and overall page load time. Each call to ReactDOM.render() initializes a React instance, which involves parsing JSX, setting up event listeners, and rendering components. With hundreds of these instances, this process can become very slow, especially on lower-end devices or browsers.

You may notice longer initial load times as well as sluggish interactions, as the browser has to handle many React instances, each managing its own state, events, and rendering cycle. Additionally, memory consumption could increase, as each instance may store redundant information in memory, contributing to slowdowns.

To improve performance, consider alternatives like:

Lazy loading: Only render components when they’re needed (e.g., when they enter the viewport). React’s Concurrent Mode: This can help manage rendering and improve performance by prioritizing updates. Component-level state management: Instead of initializing React for each interactive piece, you can group similar components to reduce the number of ReactDOM.render() calls. Learn more about optimizing React performance and techniques for efficient component rendering.