Progressive Web Application Development by Example

Polyfilling fetch in legacy browsers

Fetch and other modern APIs enjoy broad support by major browsers. However, there is still enough users using older browsers. Many enterprises still require employees to use obsolete versions of Internet Explorer. Many consumers that are happy with older phones and do not upgrade their devices or update software often.

This means we need to make our websites adaptable to these potential scenarios. Fortunately, many APIs can be polyfilled with JavaScript libraries. Fetch and promises are modern features that can easily be polyfilled.

Just like we feature detect service worker support, we can feature detect fetch and promise support. If those features are not supported, we can then load a polyfill. It is ...