# Finding the rotation of an array in JavaScript

JavascriptWeb DevelopmentFront End TechnologyObject Oriented Programming

We are required to write a JavaScript function that takes in an array and a number n.

Our function should rotate the array by n elements, i.e., take n elements from the front and put them to the end.

The only condition here is that we have to do this without using any extra space in memory −

For example −

If the input array is the following,

const arr = [12, 6, 43, 5, 7, 2, 5];

and number n is 3, then the output should be;

const output = [5, 7, 2, 5, 12, 6, 43];

## Example

Following is the code −

const arr = [12, 6, 43, 5, 7, 2, 5];
const num = 5;
const rotateByOne = arr => {
for(let i = 0; i < arr.length-1; i++){
temp = arr[i];
arr[i] = arr[i+1];
arr[i+1] = temp;
};
}
Array.prototype.rotateBy = function(n){
const { length: l } = this;
if(n >= l){
return;
};
for(let i = 0; i < n; i++){
rotateByOne(this);
};
};
arr.rotateBy(num);
console.log(arr);

## Output

This will produce the following output in console −

[
2, 5, 12, 6,
43, 5,  7
]