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JavaScript Array reduceRight() Method

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  • Last Updated : 04 Oct, 2021
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Below is the example of Array reduceRight() method. 

  • Example: 

HTML




<!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>          

Output: 
 

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.  

HTML




<!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>                    

Output: 
 

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

HTML




<!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 reduceRight 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>                    

Output: 
 

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

  • Google Chrome 3
  • Microsoft Edge 12
  • Mozilla Firefox 3.0
  • Safari 5
  • Opera 10.5
  • Internet Explorer 9

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