Array reduceRight()

reduceRight() is reduction method. reduceRight() iterates all items and build up a value for return. reduceRight() starts at the last and travels toward the first.

reduceRight() accepts two arguments:

a function to call on each item
an optional initial value

The function passed into reduceRight() accepts four arguments:

the previous value,
the current value,
the item's index,
the array object.

The returned value from the function is passed in as the first argument for the next item. The first iteration occurs on the second item in the array.

The reduceRight() method works in the same way, just in the opposite direction.

 
<!DOCTYPE html>
<html>
<head>
    <title>Example</title>
    <script type="text/javascript">
        var values = [1,2,3,4,5]; 
        
        var sum = values.reduceRight(function(prev, cur, index, array){
             return prev + cur; 
        }); 
        
        document.writeln(sum); //15 
       
    </script>
</head>
<body>
</body>
</html>

Click to view the demo