JavaScript | Uint8Array.from() Method

Last Updated : 28 Jan, 2020

The Uint8Array array represents an array of 8-bit unsigned integers. By default, the contents of Uint8Array are initialized to 0.

The Uint8Array.from() method is used to create a new Uint8Array from an array-like or iterable object. So when you want to convert an arrayLike or iterable object then you can be used this function by passing the object as a parameter to this function along with map function and value used for map function if needed.

Syntax:

Uint8Array.from( source, mapFn, thisArg )

parameters: This method accept three parameters as mentioned above and described below:

source: This parameter contains an array-like or iterable object which is used to convert to a Uint8Array object.
mapFn: It is an optional parameter which is Map function to call on every element of the Uint8Array array.
thisArg: It is an optional parameter which store the value to use as this when executing mapFn.

Return Value: This method returns a new Uint8Array instance.

Below example illustrate the working of Uint8Array.from() method in JavaScript:

Program 1:

<script>
  
// Create a Uint8Array from a string like structure
var  array = Uint8Array.from('45465768654323456');
  
// Print the result
document.write(array);
</script>

Output:

4, 5, 4, 6, 5, 7, 6, 8, 6, 5, 4, 3, 2, 3, 4, 5, 6

Program 2:

<script>
  
// Create a Uint8Array from a array by adding
// 3 to each number using function
var  array = Uint8Array.from([1, 2, 3, 4, 5, 6], z => z+3);
  
// Print the result
document.write(array);
</script>

Output:

4, 5, 6, 7, 8, 9

References: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/from

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