Compact vars branch now merged

Could be useful to force old 16 byte way via some define

Yes, good point...

Can it take more memory in some cases?

Yes... The main ones I can think of are:

• Arrays with numbers between -32768 and 32767 would be able to pack both the index and value into one variable. Now that number is lower - I guess between -2048 and 2047 on most boards.
  
• Non-flat strings aren't quite as efficient now. Each extra bit of string has an overhead of 4 bytes, so now the blocks are smaller it's roughly 30% overhead, not 25%.
  
  

However in reality I don't think much of that matters. Any String that you actually allocate in one chunk that's big enough gets turned into a flat string now, where the overhead is just one JsVar of 13 bytes (where previously it was 16 bytes).

And generally if you're storing a lot of numbers in an array you should probably have been using typed arrays anyway :)

can we have one or two more bits for array size so typed arrays over 64k are possible

Can you file an issue for this? I think worst case I should be able to add some bits from JsVarDataArrayBufferViewType to get us up to 256k.