Rotate an array by k positions in JavaScript

This post will discuss how to rotate an array by k positions in JavaScript.

There are several ways to rotate an array in JavaScript, depending on the direction and the number of times we want to rotate the elements. Rotating an array means shifting the elements to the left or right and putting them back on the opposite end of the array. For example, if we have an array [1, 2, 3, 4] and we want to rotate it to the right by one position, we will get [4, 1, 2, 3]. Some of the common functions to rotate an array in JavaScript are:

1. Using `pop()` and `unshift()` functions

These functions allow us to remove the last element of an array and add it to the beginning, or vice versa. We can use them in a loop to rotate the array by a given number of times. Here’s an example:

// rotate the array to the right by k positions

function rotateRight(arr, k)

{

for (let i = 0; i < k; i++) {

// remove the last element and add it to the beginning

arr.unshift(arr.pop());

}

return arr;

}

let arr = [1, 2, 3, 4, 5];

// rotate an array to the right by 3 positions

let rotatedArray = rotateRight(arr, 3);

console.log(rotatedArray); // [3, 4, 5, 1, 2]

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2. Using `slice()` and `concat()` functions

These functions allow us to create a shallow copy of a part of an array and join two or more arrays together. We can use them to split the array into two parts and swap their positions. Here’s an example:

// rotate the array to the left by k positions

function rotateLeft(arr, k)

{

// get the length of the array

let n = arr.length;

// get the index where to split the array

let index = k % n;

// slice the array into two parts and concat them in reverse order

return arr.slice(index).concat(arr.slice(0, index));

}

let arr = [1, 2, 3, 4, 5];

// rotate an array to the left by 3 positions

let rotatedArray = rotateLeft(arr, 3);

console.log(rotatedArray); // [4, 5, 1, 2, 3]

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3. Using `reverse()` function

This function reverses the order of the elements in an array. We can use it to reverse the whole array and then reverse each part separately. Here’s an example:

// rotate the array to the right by k positions

function rotateRight(arr, k)

{

// get the length of the array

let n = arr.length;

// get the index where to split the array

let index = n - (k % n);

// reverse the whole array

arr.reverse();

// reverse each part separately

arr.reverse(0, index - 1);

arr.reverse(index, n - 1);

return arr;

}

let arr = [1, 2, 3, 4, 5];

// rotate an array to the right by 3 positions

let rotatedArray = rotateRight(arr, 3);

console.log(rotatedArray); // [5, 4, 3, 2, 1]

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That’s all about rotating an array by k positions in JavaScript.

Rotate an array by k positions in JavaScript

1. Using pop() and unshift() functions

2. Using slice() and concat() functions

3. Using reverse() function

Share this:

1. Using `pop()` and `unshift()` functions

2. Using `slice()` and `concat()` functions

3. Using `reverse()` function