Convert Uint8Array to Array in Javascript

Question

I have Uint8Array instance that contains binary data of some file.
I want to send data to the server, where it will be deserialized as byte[].
But if I send Uint8Array, I have deserialization error.

So, I want to convert it to Array, as Array is deserialized well.
I do it as follows:

    function uint8ArrayToArray(uint8Array) {
        var array = [];

        for (var i = 0; i < uint8Array.byteLength; i++) {
            array[i] = uint8Array[i];
        }

        return array;
    }

This function works fine, but it is not very efficient for big files.

Question: Is there more efficient way to convert Uint8Array --> Array?

ismail simsek · Accepted Answer · 2020-04-15 17:59:09Z

121

You can use the following in environments that support Array.from already (ES6)

var array = Array.from(uint8Array)

When that is not supported you can use

var array = [].slice.call(uint8Array)

edited Apr 15, 2020 at 17:59

ismail simsek

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answered Apr 16, 2015 at 13:56

darthmaim

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4 Comments

Kysil Ivan Over a year ago

Yes , [].slice works fine, and it is more compact. But it seems not more efficient. Takes ~5 sec for 10mb file. (

Kysil Ivan Over a year ago

.entries() (and/or .values()) returns ArrayIterator object, not array.

jordancpaul Over a year ago

Nitpicking here, but you're just a tiny bit better off calling Array.prototype.slice.call instead of [].slice as it saves an unnecessary array construction.

cmcnphp Over a year ago

I just wanna say that even 6 years later this is perfect. My 6 million line file takes just seconds.

Vinicio Ajuchan · Accepted Answer · 2015-04-16 14:15:12Z

-2

There is a method of Uint8Array using the prototype (but it only supported by Firefox and Chrome):

TypedArray.prototype.entries() --> it returns a array.

Check it out: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/entries

answered Apr 16, 2015 at 14:15

Vinicio Ajuchan

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2 Comments

Kysil Ivan Over a year ago

No, it is ArrayIterator object. Read in link.

Vinicio Ajuchan Over a year ago

Ooo, I see, my mistake ! sorry to don't be helpful for you! Good luck!

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