I always thought Smalltalk seemed like a closer match to JS than Scheme, if you got rid of first-class message passing. How much overhead is there? For example in Objective-J in reasonably tight loops, I usually try to avoid message passing or using the Cappuccino types if I can. JS is already pretty slow in IE and older browsers, and UI updates can become noticeably slower with more overhead.
There's no overhead, in the sense that one Smalltalk message send maps to one Javascript method call. However, Smalltalk tends to use more, smaller methods, and more blocks, so there's some stylistic overhead that will make idiomatic Clamato slower than idiomatic Javascript.
