JavaScript Array reduceRight() Method

Definition and Usage

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

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

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

Note:No operation is performed on array elements without values reduceRight() Method.

Instance

Example 1

Subtract the numbers in the array 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

Example 2

Subtract numbers from right to left and display the total:

<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

Syntax

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

parameter value

Parameter Description
function(total, currentValue, index, arr) Required. A function to be run for each element in the array.

Function parameters:

Parameter Description
total Required. initialValue, or the value returned by the function previously.
currentValue Required. The value of the current element.
index Optional. The array index of the current element.
arr Optional. The array object to which the current element belongs.
initialValue Optional. The value passed as the initial value to the function.

Technical details

Return value: Returns the accumulated result of the last call to the callback function.
JavaScript version: ECMAScript 5

Browser support

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

All browsers fully support this method. reduceRight() Method:

Chrome IE Edge Firefox Safari Opera
Chrome 3 IE 9 Edge 12 Firefox 3 Safari 5 Opera 10.5
June 2009 September 2010 July 2015 January 2009 June 2010 March 2010

Related page

Tutorial:JavaScript Array

Tutorial:JavaScript Array Const

Tutorial:JavaScript Array Methods

Tutorial:JavaScript Array Sorting

Tutorial:JavaScript Array Iteration

Manual:Array.reduce() Method