Intelligently load polyfills

Feature Request

- [ ] bug report -> please search issues before submitting
- [x] feature request

Versions.

future

Desired functionality.

Apologies if this already tracked somewhere I couldn’t find it/ At the moment all polyfills are loaded into all browsers, it would be awesome if we could only load the polyfills that are needed by the browser the app is running in. This would help will smaller overall payload size for more modern browsers and keep legacy browsers working without having to manually manage the polyfills.ts file.

Additional information

Article for reference: https://philipwalton.com/articles/loading-polyfills-only-when-needed/

Initial thoughts

1. a script could be inlined (maybe) to load the polyfills that we know for sure angular requires
2. the initial bootstrapping would need to wait until the polyfills were loaded or even better, not loaded. (reference bottom of the referenced article)
3. polyfills.ts would still exist but would only be used to load zone.js and additional polyfills that the user wants to add.

[clydin]

Support for this will be available in CLI version 7.3 currently in release candidate stage. An overview of the functionality can be found in the PR description found here: https://github.com/angular/angular-cli/pull/13403

[dharapvj]

See how angular.io website splits IE polyfills out… Issue Fix

Can something like this be implemented? It does not seem very difficult.