How to use polyfills in your React app

Polyfills are essential tools for JavaScript developers who want to use modern features while ensuring compatibility with older browser versions. A polyfill provides a fallback that mimics the desired behavior using supported APIs, allowing developers to use new JavaScript features like String.padEnd even when some browsers do not support them natively. This article explores using polyfills in React applications, demonstrating how to write a polyfill from scratch and how to utilize libraries such as Polyfill.io and core-js to handle polyfills without manual coding. It also highlights the importance of ensuring application security, particularly in light of recent reports of Polyfill.io being compromised to spread malware. Through practical examples, the article illustrates how developers can include polyfills in projects via CDNs or npm packages, ensuring that applications run smoothly across various browser versions.