Array reduceRight()

In this chapter you will learn:

How to reduce a Javascript array from the end

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><!--from  ja  va 2 s  .com-->
<html>
<head>
    <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

Next chapter...

What you will learn in the next chapter:

How to reverse a Javascript array

Array reduceRight()