If you're going to use
DataView for your binary data and carry binary data as base64 strings, you can use the Mozilla-written functions at https://developer.mozilla.org/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding#Solution_.232_.E2.80.93_rewriting_atob%28%29_and_btoa%28%29_using_TypedArrays_and_UTF-8 to do so. They provide the functions
UTF8ArrToStr to perform UTF-8 encoding and decoding, as well as
base64DecToArr to convert between base64 strings and array buffers.
Here's an interconversion example that encodes a text string as UTF-8, then converts the text into base64, then shows the base64 results, and finally converts ...