**`reduceRight()`** is a higher-order function that accumulates or reduces all the values in an array to a single value through the application of a binary function to each of the values, starting from right to left.

`reduceRight()` is useful when the order of operation on the array *does* matter. However, if the operation is commutative, then one may simply use the `reduce()` function instead.

# Prototype
```javascript
array.reducRight((accumulator, currentValue, index, array)=>{}, initialValue)
```
# Parameters
* `callbackfn`: The callback function that is executed on each of the values in the array. `callbackfn` takes in 4 additional arguments:
    
   * `accumulator`: The **`accumulator`** holds the accumulated result of applying the `callbackfn` to the list. `accumulator` is initialized with `initial Value` if an initial value is supplied.
    * **`current value`**: The current value being processed in the array.
    * **`index`** (optional): The index of the current value being processed. The `index` starts from $0$ if the `inital Value` is provided, otherwise, it starts at $1$.
    * **`array`** (optional): The array on which `reduce()` is called upon.

* **`initalValue`** (optional):  `initialValue` is used as the first value for the `reduce()` operation. If it is not supplied, then the first value at index $0$ is used as the `accumulator`.

# Return value
`reduce()` returns the accumulated result of applying the function on each of the elements in the array.

# Code

const numbers = [1 ,2 ,3]

const product1 = numbers.reduce((x, y) => x / y);
const product2 = numbers.reduceRight((x, y) => x / y);

console.log(product1, product2)

Here, we demonstrate the difference in the `reduce()` and `reduceRight()` functions. Since we used the division operation, which is non-commutative, the order of operation matters. 

The `reduce()` function applies the division function from left to right while the `reduceRight()` operation goes from right to left, which gives a different result.

What is array reduceRight() in Javascript?

Accumulates array values to a single value from right-to-left using a callback function.