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

javascript arrays filereader typed-arrays
Derek picture Derek · May 2, 2016 · Viewed 15.1k times · Source

I have a typed array full of binary data that is being generated from an ArrayBuffer

var myArr = new Uint8Array(myBuffer);

I am presenting this to the user with 

var blob = new Blob(myArr, {type: "octet/stream"};
var blobURL = URL.createObjectURL(blob);

and inserting a link that is

"<a href=" + blobUrl + " download=" + filename "/a>"

Later, I am letting the user select the file from disk, and using a file reader to do with

var reader = new FileReader();

reader.onload = function () {
console.log(reader.result);
};

reader.readAsArrayBuffer(sourceFile);

The problem is, it seems like no matter what I do, I get a "string" of the file's contents. In fact, when I save the file, I can open it, and it is plainly human readable. I.E. if my Uint8Array was {"0" : "51", "1" : "52", "2" : "53" }

I can open the downloaded blob in a text editor and I just see "515253" which I don't think is what should be happening.

How can I make a link to a file download for my file that is formatted properly so I can read it back in an dget the right values?

Answer

Derek picture Derek · May 4, 2016

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?

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