The reduceRight() method of TypedArray instances applies a function against an accumulator and each value of the typed array (from right-to-left) to reduce it to a single value. This method has the same algorithm as Array.prototype.reduceRight().

Try it

const uint8 = new Uint8Array([10, 20, 30]);

const result = uint8.reduceRight(
  (accumulator, currentValue) => `${accumulator}, ${currentValue}`,
);

console.log(result);
// Expected output: "30, 20, 10"

Syntax

reduceRight(callbackFn)
reduceRight(callbackFn, initialValue)

Parameters

callbackFn

A function to execute for each element in the typed array. Its return value becomes the value of the accumulator parameter on the next invocation of callbackFn. For the last invocation, the return value becomes the return value of reduceRight(). The function is called with the following arguments:

accumulator

The value resulting from the previous call to callbackFn. On the first call, its value is initialValue if the latter is specified; otherwise its value is the last element of the typed array.

currentValue

The value of the current element. On the first call, its value is the last element if initialValue is specified; otherwise its value is the second-to-last element.

currentIndex

The index position of currentValue in the typed array. On the first call, its value is array.length - 1 if initialValue is specified, otherwise array.length - 2.

array

The typed array reduceRight() was called upon.

initialValue Optional

Value to use as accumulator to the first call of the callbackFn. If no initial value is supplied, the last element in the typed array will be used and skipped. Calling reduceRight() on an empty typed array without an initial value creates a TypeError.

Return value

The value that results from the reduction.

Description

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

Examples

Sum up all values within an array

const total = new Uint8Array([0, 1, 2, 3]).reduceRight((a, b) => a + b);
// total === 6

Specifications

Browser compatibility

See also

• Polyfill of TypedArray.prototype.reduceRight in core-js
• JavaScript typed arrays guide
• TypedArray
• TypedArray.prototype.map()
• TypedArray.prototype.reduce()
• Array.prototype.reduceRight()
• Object.groupBy()
• Map.groupBy()