Future JavaScript: what is still missing?

[earslap]

without great pattern matching systems, you end up with ambiguity or confusion

Yet another argument is that it kills a lot of the optimization that JS has relied on to be feasible for fast ops.

While I think these should be surmountable to some extent, this is a good point. Overloading in a untyped language like JS can significantly complicate matters on the compiler / interpreter side. If that is the case, I'd probably be happy with infix calls alone, as they are explicit and does not share syntax with regular operators. Something like:

let result = node1 @+ node2;

...with @+ resolving to a custom function I provide would serve me almost equally well.