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JavaScript Array reduceRight() Method


Example

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

var numbers = [175, 50, 25];

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

function myFunc(total, num) {
  return total - num;
}
Try it Yourself »

More "Try it Yourself" examples below.


Definition and Usage

The reduceRight() method reduces the array to a single value.

The reduceRight() method executes a provided function for each value of the array (from right-to-left).

The return value of the function is stored in an accumulator (result/total).

Note: reduceRight() does not execute the function for array elements without values.


Browser Support

The numbers in the table specify the first browser version that fully supports the method.

Method
reduceRight() Yes 9.0 3.0 4 10.5

Syntax

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

Parameter Values

Parameter Description
function(total, currentValue, index, arr) Required. A function to be run for each element in the array.
Function arguments:
Argument Description
total Required. The initialValue, or the previously returned value of the function
currentValue Required. The value of the current element
currentIndex Optional. The array index of the current element
arr Optional. The array object the current element belongs to
initialValue Optional. A value to be passed to the function as the initial value


Technical Details

Return Value: Returns the accumulated result from the last call of the callback function
JavaScript Version: ECMAScript 5

More Examples

Example

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

<button onclick="myFunction()">Try it</button>

<p>Sum of numbers in array: <span id="demo"></span></p>

<script>
var numbers = [2, 45, 30, 100];

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

function myFunction(item) {
  document.getElementById("demo").innerHTML = numbers.reduceRight(getSum);
}
</script>
Try it Yourself »

Related Pages

JavaScript Tutorial: JavaScript Arrays

JavaScript Tutorial: JavaScript Iteration

JavaScript Reference: JavaScript reduce() Method