The copyWithin() method of TypedArray instances shallow copies part of this typed array to another location in the same typed array and returns this typed array without modifying its length. This method has the same algorithm as Array.prototype.copyWithin().

Try it

const uint8 = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8]);

// Insert position, start position, end position
uint8.copyWithin(3, 1, 3);

console.log(uint8);
// Expected output: Uint8Array [1, 2, 3, 2, 3, 6, 7, 8]

Syntax

copyWithin(target, start)
copyWithin(target, start, end)

Parameters

target

Zero-based index at which to copy the sequence to, converted to an integer. This corresponds to where the element at start will be copied to, and all elements between start and end are copied to succeeding indices.

start

Zero-based index at which to start copying elements from, converted to an integer.

end Optional

Zero-based index at which to end copying elements from, converted to an integer. copyWithin() copies up to but not including end.

Return value

The modified typed array.

Description

See Array.prototype.copyWithin() for more details. This method is not generic and can only be called on typed array instances.

Examples

Using copyWithin()

const buffer = new ArrayBuffer(8);
const uint8 = new Uint8Array(buffer);
uint8.set([1, 2, 3]);
console.log(uint8); // Uint8Array [ 1, 2, 3, 0, 0, 0, 0, 0 ]
uint8.copyWithin(3, 0, 3);
console.log(uint8); // Uint8Array [ 1, 2, 3, 1, 2, 3, 0, 0 ]

Specifications

Browser compatibility

See also

• Polyfill of TypedArray.prototype.copyWithin in core-js
• JavaScript typed arrays guide
• TypedArray
• Array.prototype.copyWithin()