This repository is a fork of https://github.com/antimatter15/bzip2.js that makes the functionality asynchronous.
It's actually pretty simple to use, you can pass your Uint8Array to the bzip2.array method to get a bit reader function. This bit reader function is what all the other methods, header, decompress, and simple use.
header(bitstream) quite obviously reads in the bzip2 file header. It returns a single number between 1 and 9 describing the block size, which is one of the arguments of decompress
decompress(bitstream, size[, len]) does the main decompression of a single block. It'll return -1 if it detects that it's the final block, otherwise it returns a string with the decompressed data. If you want to cap the output to a certain number of bytes, set the len argument.
simple(bitstream) is what you probably want to use, because it combines header and loops over decompress so that the entire file is decompressed and returned as a string.
array(typed_array) is the function that generates that mythical bitstream function from a standard Uint8Array which you can make from an array buffer with new Uint8Array(arraybuffer).