What is the use of polyfills.ts file in Angular

Basically polyfills compatible for different browsers especially IE old versions IE8, IE9 and IE10. Angular has new features which written in ES6 and typescript, so polyfills helps to compatible with different browsers.

Polyfills in angular are few lines of code which make your application compatible for different browsers. The code we write is mostly in ES6(New Features: Overview and Comparison) and is not compatible with IE or firefox and needs some environment setups before being able to be viewed or used in these browsers.

Polyfills.ts was provided by angular to help you do away with need to specifically setup everything.

From Docs

Angular is built on the latest standards of the web platform. Targeting such a wide range of browsers is challenging because they do not support all features of modern browsers.

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