JavaScript Array reduceRight() Method

Below is the example of Array reduceRight() method.

  • Example:
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    <!DOCTYPE html>
    <html>
          
    <head>
        <title>
            JavaScript Array reduceRight() Method
        </title>
    </head>
      
    <body style="text-align:center;">
          
        <h1 style="color: green;">GeeksforGeeks</h1>
          
        <p>
            Click here to get the Subtract
            of array elements from the left side
        </p>
          
        <button onclick="myGeeks()">
            Click Here!
        </button>
          
        <br><br>
          
        Subtract: <span id="GFG"></span>
          
        <!-- Script to use reduceRight method -->
        <script>
            var arr = [175, 50, 25];
      
            function subofArray(total, num) {
                return total - num;
            }
            function myGeeks(item) {
                document.getElementById("GFG").innerHTML
                        = arr.reduceRight(subofArray);
            }
        </script>
    </body>
      
    </html>          

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  • Output:
    
Image
    • 



The arr.reduceRight() method in JavaScript is used to convert elements of the given array from right to left to a single value.


Syntax:


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


Parameter: This method accepts five parameters as mentioned above and described below:


    

  • function(total, currentValue, index, arr): It is the required parameter and used to run for each element of array. It contains four parameter which are listed below:

      

    • total: It is required parameter and used to specify the initialValue, or the previously returned value of the function.
      • 

    • currentValue: It is required parameter and used to specify the value of the current element.
      • 

    • currentIndex: It is optional parameter and used to specify the array index of the current element.
      • 

    • arr: It is optional parameter and used to specify the array object the current element belongs to.
      • 

    

    • 

  • initialValue: It is optional parameter and used to specify the value to be passed to the function as the initial value.
    • 



Example 1: This example use reduceRight() method to return the subtract of all array elements from right. 













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<!DOCTYPE html> 


<html> 


      


<head> 


    <title> 


        JavaScript Array reduceRight() Method 


    </title> 


</head> 


  


<body style="text-align:center;"> 


      


    <h1 style="color: green;">GeeksforGeeks</h1> 


      


    <p> 


        Click here to get the Subtract 


        of array elements from right 


    </p> 


      


    <button onclick="myGeeks()"> 


        Click Here! 


    </button> 


      


    <br><br> 


      


    Subtract: <span id="GFG"></span> 


      


    <!-- Script to use reduceRight method -->


    <script> 


        var arr = [10, 20, 30, 40, 50, 60]; 


  


        function subofArray(total, num) { 


            return total - num; 


        } 


        function myGeeks(item) { 


            document.getElementById("GFG").innerHTML 


                    = arr.reduceRight(subofArray); 


        } 


    </script> 


</body> 


  


</html>                  



















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Output:

Image


Example 2: This example use reduceRight() method to return the round sum of all array elements. The code performing sum that does not effect by the reduceRight() method.











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<!DOCTYPE html> 


<html> 


      


<head> 


    <title> 


        JavaScript Array reduceRight() Method 


    </title> 


</head> 


  


<body style="text-align:center;"> 


      


    <h1 style="color: green;">GeeksforGeeks</h1> 


      


    <p> 


        Click here to get the sum 


        of array elements 


    </p> 


      


    <button onclick="myGeeks()"> 


        Click Here! 


    </button> 


      


    <br><br> 


      


    Sum: <span id="GFG"></span> 


      


    <!-- Script to use reduce method -->


    <script> 


        var arr = [1.5, 20.3, 11.1, 40.7]; 


   


        function sumofArray(sum, num) { 


            return sum + Math.round(num); 


        } 


        function myGeeks(item) { 


            document.getElementById("GFG").innerHTML 


                    = arr.reduceRight(sumofArray, 0); 


        } 


    </script> 


</body> 


  


</html>                     



















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Output:

Image

Supported Browsers: The browsers supported by JavaScript Array reduceRight() method are listed below:


    

  • Google Chrome 
    • 

  • Microsoft Edge 9.0
    • 

  • Mozilla Firefox 3.0
    • 

  • Safari 4.0
    • 

  • Opera 10.5
    • 



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