We're using this helper function when reading data from the [`PDFWorkerStreamReader.read`](a49d1d1615/src/core/worker_stream.js (L90-L98)
) and [`PDFWorkerStreamRangeReader.read`](a49d1d1615/src/core/worker_stream.js (L122-L128)
) methods, and as can be seen they always return `ArrayBuffer` data. Hence we can simply get the `byteLength` directly, and don't need to use the helper function. Note that at the time when `arrayByteLength` was added we still supported browsers without TypedArray functionality, and we'd then simulate them using regular Arrays.