ES6-only polyfills

[vkrol]

Hello! Thank you for your work.

Can you explain me, please, why you are not provide ES6-only polyfills? If I need to support only ES5 (not ES3) runtimes, why I need to include ES5 polyfills in my bundle when I imported "core-js/es6" entry point?
I read the changelog to the 2.1.0 version (https://github.com/zloirock/core-js/releases/tag/v2.1.0, section "Separated ES5 polyfills moved to the ES6 namespace. Why?"), but still do not understand.

Thanks!

[zloirock]

ES6 changes behavior most added in ES5 features. Object methods, Array methods... almost all excluding some features like Array.isArray or Date.now. I don't see any reason implement something in the ES5 namespace with ES5 logic and after that replace or wrap it in the ES6 namespace - it's size and performance issue. Size difference with old conception for core-js/es6 should be only some percent. It's the first reason.

The second - I don't know any popular engine, completely correct by ES5 spec - they all have some bugs and core-js fixes them.

In the future, for example core-js@3, I think, ES5 / ES6 / ES7 namespaces will be removed and for ECMAScript will be available only 2 main namespaces - for stable ES and for ES proposals.

[vkrol]

Thank you for information!

[RehanSaeed]

Just to confirm that I have this right, I can currently import ES5, 6, or 7 separately:

import "core-js/es5";
import "core-js/es6";
import "core-js/es7";

According to caniuse.com ES5 is supported on all current browsers but I might still need ES5 to fix broken browser implementations?

[zloirock]

@RehanSaeed ES6 changes behaviour almost all features added in ES5, so core-js/es6 entry point includes almost all of them. Also, as you wrote, it's required for fixing broken browser implementations.

[RehanSaeed]

Do you recommend importing the es5 code if I want to support 99% of browsers or the last two versions (Including IE 10 onwards)?

[zloirock]

Depends on your goals and objectives.