Try this version out, I enabled babel. Your browser might not support class fields yet.
https://flems.io/#0=N4IgZglgNgpgziAXAbVAOwIYFsZJAOgCsEAaEAYw...
Re:Ask HN: Why is mithril.js not popular?
by foxdonut00 on Tuesday April 16, 2019 @04:20PM
(#19676950)
Seems to work fine, where are you seeing this error?
Re:Ask HN: Why is mithril.js not popular?
by itronitron on Tuesday April 16, 2019 @04:23PM
(#19676972)
i get the same error in Firefox
Edit: Seems like it's bugged? `fields are not currently supported`