How to use polyfills in Angular application?

In an Angular application, a polyfill is a piece of code that implements features that are not supported by the current browser. This allows developers to use new features of JavaScript or other web technologies without having to worry about whether or not those features are supported by the browser that the user is using to view the application.

For example, if an Angular application uses the latest version of JavaScript, but the user is viewing the application in a browser that only supports an older version of JavaScript, the polyfill will provide the missing functionality, allowing the application to run smoothly in the user's browser. This helps to ensure that the application can be used by a wider range of users, regardless of the browsers they are using.

To use polyfills in an Angular application, you can include them in your application code by adding them to the polyfills.ts file, which is located in the src/ directory of your Angular project.

To add a polyfill to the polyfills.ts file, you can either import it from a library, such as the core-js library, or you can include the polyfill directly in the file using the import statement. For example, to add the polyfill for Array.prototype.includes, you can add the following code to the polyfills.ts file:

import 'core-js/es6/array';

Alternatively, you can use a polyfill service, such as Polyfill.io, to automatically provide the necessary polyfills based on the user's browser and the features used by your Angular application. To use Polyfill.io, you can include the following script in the index.html file of your Angular project:

<script src="https://polyfill.io/v2/polyfill.min.js?features=es6"></script>

This will automatically provide the necessary polyfills for the features specified in the features parameter, which in this case is es6, indicating that the polyfills are for features from the ECMAScript 6 (ES6) specification of JavaScript. You can specify different features by adding them to the features parameter, separated by commas.

Once you have added the polyfills to your Angular application, they will be automatically loaded and used by the application when it runs in a browser. This will ensure that the application can use the latest features of JavaScript and other web technologies, even if the user's browser does not support those features natively.