I wish JavaScript had built-in immutable data structures. Immutable.js is interesting, but difficult to bring into a project because it's difficult to get buy-i

I wish JavaScript had built-in immutable data structures. Immutable.js is interesting, but difficult to bring into a project because it's difficult to get buy-in from everyone involved. I also wish JavaScript were generally better at functional programming - I'd love to see a keyword that ensures that no form of mutation is possible within a given scope.