How do I store a javascript string in byte format and for later retrieval in string form?

I want to generate a file containing strings alongside Float32Arrays in my web app. I can write this data into a blob and then a file like this:

var myFirstFloat32Array = new Float32Array([42, 1, 2, 3]);
var myString = 'This is my string. It is a beautiful string.';
var blob = new Blob([
    new Uint8Array([myFloat32Array.length]), // Store the size.
    myFloat32Array,
    new Uint8Array([myString.length]), // Store the size.
    myString);
var downloadLink = document.createElement('a');
downloadLink.href = window.URL.createObjectURL(blob);
downloadLink.download = 'generatedFile';
downloadLink.innerHTML = 'Click to download generated file.';

So ... that successfully writes the file, but how do I read the string following the float 32 array?

I can read the first float32 array easily by reading the number from the first 4 bytes (which gives me the size of the array) and then constructing a Float32Array of that length.

However, how do I read the string? The string could contain characters outside of the ASCII range, so I can't just btoa the string, convert to a Uint8Array, and then write it.

Maybe I could convert the string to a blob first, get its size from the blob, and then somehow decode it later while reading (but how do I know the character encoding used later)?

What's the standard way to store string data alongside byte data in javascript for later decoding?