Javascript - Save typed array as blob and read back in as binary data

According to Mozilla

https://developer.mozilla.org/en-US/docs/Web/API/Blob#Example_for_creating_a_URL_to_a_typed_array_using_a_blob

var blob = new Blob([typedArray.buffer], {type: 'application/octet-stream'});

As it turns out, the problem was that I had a syntax error in the creation of the Blob.

The corrected code looked like: var blob = new Blob([myArr], {type: "octet/stream"});

I'm not really sure why if I am already passing an ArrayBuffer argument. Why I need bracket notation? Seems redundant?