There's a lot I don't like about this code.  First, this is really a `diffsParser` function that's been inlined here.  We should move it to a module.  Second, prefer `Array.map` and `Array.forEach` to using variables.  Third, use separate functions for various steps below instead of for-loops 3 deep.  Fourth, we *need* to figure out how to send binary data (Uint8Array) directly from the browser to server.  There's an MDN article on this, you basically have to put your binary data in a `Blob`.  I'd rather we didn't have to convert binary data all the time, it's not efficient.