This part looks wrong:

zlib.js/zip.js at develop · imaya/zlib.js · GitHub

      for (j = 0; j < 12; ++j) {
        buffer[j] = this.encode(
          key,
          i === 11 ? (file.crc32 & 0xff) : (Math.random() * 256 | 0)
        );
      }

Specifically the condition i === 1 looks wrong. j is used in this loop. i is used in an outer loop and won't change in this loop.

This wrong condition will prevent it from correctiy storing CRC information and make the resulting file incompatible with commonly-used decompression tools.