Compatibility data seems incomplete

[implicitdef]

Hi

I've noticed that on a small JS project, when using the recommended setup of Babel with preset-env / core-js / browserslist etc., many polyfills are included, most of them I didn't think they would be necessary.

I've dug into the compatibility data. It seems to be saying that many features are not included on some browsers, contradicting the compatibility data I see on MDN or caniuse.com.

Here's a few exemples I don't understand. There are many more.

'es.array.concat': { chrome: '51', edge: '15', firefox: '48', safari: '10.0', },
Yet MDN states that it was in Chrome 1, Edge 12, Firefox 1, Safari 1
They also add IE 5.5 and some mobiles browsers.

'es.string.split': { chrome: '54', firefox: '49', safari: '10.0', },
Same thing, MDN says something different.
Are you saying that es.string.split is not present or not correctly implemented on "ie", "edge", "android" ?

'es.string.replace': { chrome: '64', },
Same thing, are you saying only Chrome 64+ implements this correctly ? Why ?
(MDN)

On a more general note, about "android" : the browserslist query I use on my project happens to include, amongst others, android 4.4.3-4.4.4.
In the data https://github.com/zloirock/core-js/blob/master/packages/core-js-compat/src/data.js, there seems to be only 4 references to "android". So this means that you're considering that Android Webview pretty much doesn't implement anything ? Why ? It doesn't seem right.

Thanks for you help

[slowcheetah]

@implicitdef this is because in many browsers there are implementations, but they do not meet the standards. For example I already described about es.string.replace in that comment

[implicitdef]

OK, thank you. Could you detail a bit more, do you know what are exactly the problems with the features I listed ?

Where could I get more information on these problems ? Maybe you maintain some kind of history or documentation ? The only other sources I know of are caniuse.com and MDN, but they don't seem to reach the same conclusion as you.

Regarding your comment in the other issue:

es.string.replace & es.string.search should refer to well-known symbols

I don't understand what it means.

[slowcheetah]

@implicitdef see official document about standards. If you want to dive deeper, you may search string 'well-known' and find table with info about well-known symbols. core-js tries to bring all implementations to the described standards.

Also for understanding you can see the tests. For example es.string.replace.js