[quink]

https://en.wikipedia.org/wiki/ECMAScript_for_XML - Firefox had it too, but people at large just didn't want it, so it got removed. It got disabled for web pages with the release of Firefox 17, 6 months prior to the first release of React.

[sltkr]

Personally I never heard about it. So it might not be that people didn't want it, but that it wasn't promoted much.

Also, it sounds like the only browser to ever support it was Firefox? That was probably much more of a limiting factor for adoption.

[kibibu]

If you weren't coding for the flash platform you would have easily missed it.

Its a shame, E4X was really nice

[mhitza]

People didn't want it because browsers didn't support it (except FF, as you noted). Some of us had our fingers crossed that other browsers would pick it up.