[sametmax]

Map are not supported by most IE version, and even IE 11 doesn't support half of the API. The android browser doesn't support it at all either. Bottom line, you couldn't not have used Map during the last past years, and used objects for dict.

[bloomca]

Not too much people write plain JS anymore, and it is not that hard to build transpiling pipeline. Sometimes you have a small project and you don't want to deal with all this nonsense, but then you are writing code in one file and it is very small jquery style enhancements.

So, if you need objects as keys in dictionaries, then there is a big chance that you can use transpiling already (modules, other ES6 features).

Please, don't take it as an offence, just a suggestion – I really don't see a problem here.