I think if you wanted to make this really robust, you could use more techniques to beef it up. One technique would be to store verbose or commonly-used string

I think if you wanted to make this really robust, you could use more techniques to beef it up. One technique would be to store verbose or commonly-used string constants in accessible locations like Array.prototype.f. Then you could access, say, the string "prototype" by simply writing [][(![]+[])[+[]]] Once you build up a little scratch storage of the most common or hard-to-encode strings, everything starts getting orders of magnitude smaller. (Technically, this means that you're polluting the space shared with the program being encoded, so for everything to work the program can't make use of it. But that's a pretty simple invariant to ask of the input program: "don't get or set the 'f' property of arrays.") Another technique would be to break up large statements into smaller substatements, to avoid fixed limits of JS engines on statement size. You can always avoid semicolons, since ASI is guaranteed to work if you start your statement with a !. Dave