Collapses not working on IE11

[adrigm]

SCRIPT5007: Object.keys: the argument is not an object.

[razh]

This is because Babel improved its compliance with spec behavior:

babel/babel#7034

And the _objectSpread helper function uses Object.keys.

https://github.com/babel/babel/blob/v7.0.0-beta.44/packages/babel-helpers/src/helpers.js#L373-L391

To resolve this, loose mode could be used:

https://github.com/babel/babel/tree/master/packages/babel-plugin-proposal-object-rest-spread#loose

[Herst]

Is this not what Babel is supposed to prevent? 🙄 I thought the idea was: You just write your code utilizing the newest features and we do the rest to make it work in older browsers or warn you if it is not possible…

Anyway, alternatively users targeting browsers without Object.keys support could be asked to add a shim. What else would need to be shimmed in order to support IE11? Object.assign perhaps? In that case this note would have to be added to the general browser support page and not just the sub pages of the affected features.

[XhmikosR]

/CC @Johann-S

[razh]

Wait a minute, IE 9 and above support Object.keys, but it appears their implementation is the ES5 version.

In ES5, if the argument to this method is not an object (a primitive), then it will cause a TypeError. In ES2015, a non-object argument will be coerced to an object.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys#Notes

This error is occurring because of this line:

bootstrap/js/src/collapse.js

Line 334 in 8f7bd41

...typeof config === 'object' && config

If config is not an object, this is false. In IE, Object.keys(false) results in an error, while modern browsers return [].

[japrogramer]

IE .. always slowing developers down .. it's just a shame thats all.