TypeScript Array reduceRight() Method

The Array.prototype.reduceRight() method is a built-in TypeScript function used to apply a reducer function to each element of the array, processing the elements from right to left, ultimately reducing the array to a single value.

Syntax:

array.reduceRight(callback[, initialValue])

Parameters

• callback: The function to execute on each element in the array. It takes the following arguments:
  • previousValue: The value resulting from the previous call to the callback.
  • currentValue: The current element being processed.
  • currentIndex: The index of the current element being processed.
  • array: The array reduceRight was called upon.
• initialValue (optional): The initial value to use as the first argument to the first call of the callback.

Return Value: This method returns the reduced right single value of the array. 

Examples of Array reduceRight() Method

Example 1: Reducing an Array to a Single Value

In this example, we use reduceRight() to subtract all elements of the array from the rightmost element to the leftmost element.

const array1: number[] = [1, 2, 3, 4, 5];
const result1: number = array1.reduceRight((acc: number, curr: number) => acc - curr);

console.log(result1);

Output: 

-3

Example 2: Calculating a Product in Reverse Order

In this example, reduceRight() is used to calculate the product of all elements in the array, starting from the rightmost element.

const array2: number[] = [2, 4, 8];
const result2: number = array2.reduceRight((acc: number, curr: number) => acc * curr, 1);

console.log(result2);

Output: 

64

The reduceRight() method is a powerful tool for performing reductions on arrays from right to left. It can be used for various operations, such as summing, multiplying, and concatenating elements, making it a versatile method in TypeScript.