There are still many features of bit arrays that are not yet implemented on the javascript target. We want to have all of them eventually, but it's a lot to implement in one go, and a lot to have a separate issue for each one. So I've decided to create a tracking issue to list them all, and these can be slowly ticked off when people implement specific features.

• Non byte-aligned access
• Non-constant sizes when pattern matching: <<bits:size(some_variable)>>
• Non byte-aligned segments
• Non-utf8 strings: utf16, utf32, utf16_codepoint and utf32_codepoint
• Pattern matching on utf8_codepoint, utf16_codepoint and utf32_codepoint
• Signedness: signed and unsigned
• Endianness: Missing native
• Unit specification: unit
• 16-bit floats

Please let me know if I've missed any. I'm not super familiar with bit array syntax so I mostly just looked through the compiler and found where an error was thrown on javascript.