JavaScript Array reduceRight()

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Examples

Subtract the numbers in the array, starting from the end:

const numbers = [175, 50, 25];

document.getElementById("demo").innerHTML = numbers.reduceRight(myFunc);

function myFunc(total, num) {
return total - num;
}

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Subtract the numbers, right-to-left, and display the sum:

const numbers = [2, 45, 30, 100];
document.getElementById("demo").innerHTML = numbers.reduceRight(getSum);

function getSum(total, num) {
return total - num;
}

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Definition and Usage

The reduceRight() method executes a reducer function for each array element.

The reduceRight() method works from right to left.

The reduceRight() method returns a single value: the function's accumulated result.

The reduceRight() method does not execute the function for empty elements.

Note

At the first callback, there is no return value from the previous callback.

Normally, the last array element is used as initial value, and the iteration starts from the element before.

If an initial value is supplied, this is used, and the iteration starts from last element.

Syntax

array.reduceRight(function(total, currentValue, currentIndex, arr), initialValue)

Parameters

Parameter

Description

function()

Required.
A function to be run for each element in the array.

Reducer function parameters:

total	Required. The initialValue, or the previously returned value of the function.
currentValue	Required. The value of the current element.
currentIndex	Optional. The index of the current element.
arr	Optional. The array the element belongs to.