What are Pollyfills and Why Angular need Polyfills?

A polyfill is a piece of code (usually JavaScript) that provides modern functionality on older browsers that do not support certain features of the language or web standards.

Essentially, a polyfill mimics the behavior of newer features or APIs that might not be available in older environments by implementing them in a way that older browsers can understand.

For example, modern JavaScript features like Promise, fetch, or Array.prototype.includes might not be supported in older versions of Internet Explorer or Safari. A polyfill would provide an implementation of these features for those older browsers, allowing developers to use modern features without worrying about browser compatibility.

Why Does Angular Need Polyfills?

Angular, as a modern web framework, often relies on newer JavaScript features and APIs to provide performance improvements, functionality, and ease of development. However, not all browsers support these newer features, especially older browsers. To ensure that Angular applications work correctly across all browsers, including older ones, it uses polyfills.

Here are some key reasons why Angular uses polyfills:

• Cross-Browser Compatibility: Angular needs to work in a variety of browsers, including older ones. For example, Internet Explorer (IE) and older versions of Safari don’t fully support newer JavaScript features. Without polyfills, users of these browsers would encounter errors or experience broken functionality.
• Modern JavaScript Features: Angular makes use of features like Promise, Object.assign, Map, Set, Array.prototype.includes, and others that are available in modern JavaScript but may not be present in older browsers. Polyfills allow developers to use these features in their applications while still ensuring compatibility across all browsers.
• Browser API Support: Angular also uses newer browser APIs (such as IntersectionObserver or CustomElements) that are not universally supported. Polyfills are used to fill the gap by providing a fallback implementation for browsers that do not natively support these APIs.
• Internationalization and Localization: Angular supports internationalization (i18n) and localization (l10n) features, which rely on modern browser functionality (like Intl API for date and number formatting). Polyfills help ensure that these features work consistently across different browsers.

How Does Angular Handle Polyfills?

Angular provides a polyfills.ts file in the project structure, which contains a list of polyfills required for supporting different browsers. Developers can enable or disable specific polyfills based on the target browsers they want to support. For instance, if targeting only modern browsers, some polyfills might be unnecessary and can be removed for better performance. However, if you need to support legacy browsers like Internet Explorer, you’d keep the relevant polyfills enabled.

Angular uses polyfills to ensure that modern features work seamlessly across all browsers, including older ones that lack support for new web technologies. By including polyfills, Angular can deliver a more consistent and robust experience for users, regardless of their browser version.