TypedArray.prototype.fill()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2016.

The fill() method of TypedArray instances changes all elements within a range of indices in a typed array to a static value. It returns the modified typed array. This method has the same algorithm as Array.prototype.fill().

Try it

const uint8 = new Uint8Array([0, 0, 0, 0]);
// Value, start position, end position
uint8.fill(4, 1, 3);

console.log(uint8);
// Expected output: Uint8Array [0, 4, 4, 0]

Syntax

fill(value)
fill(value, start)
fill(value, start, end)

Parameters

value: Value to fill the typed array with.
start Optional: Zero-based index at which to start filling, converted to an integer.
end Optional: Zero-based index at which to end filling, converted to an integer. fill() fills up to but not including end.

Return value

The modified typed array, filled with value.

Description

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

Examples

Using fill()

new Uint8Array([1, 2, 3]).fill(4); // Uint8Array [4, 4, 4]
new Uint8Array([1, 2, 3]).fill(4, 1); // Uint8Array [1, 4, 4]
new Uint8Array([1, 2, 3]).fill(4, 1, 2); // Uint8Array [1, 4, 3]
new Uint8Array([1, 2, 3]).fill(4, 1, 1); // Uint8Array [1, 2, 3]
new Uint8Array([1, 2, 3]).fill(4, -3, -2); // Uint8Array [4, 2, 3]

Specifications

Specification
ECMAScript® 2026 Language Specification # sec-%typedarray%.prototype.fill