Rotating an array - JavaScript

In JavaScript, rotating an array means moving elements from one position to another by a specified number of steps. This operation is useful for circular data structures and algorithmic problems.

For example, if we have an array [12, 6, 43, 5, 7, 2, 5] and rotate it by 3 positions to the left, the result would be [5, 7, 2, 5, 12, 6, 43].

Method 1: Using Array Prototype Extension

We can extend the Array prototype to add a rotation method:

// Helper function to rotate by one position
const rotateByOne = arr => {
    for(let i = 0; i = l) {
        return;
    }
    for(let i = 0; i 

[
  3, 4, 5, 6,
  7, 1, 2
]


Method 2: Using Slice and Spread Operator

A more efficient approach using array methods without modifying the prototype:

function rotateArray(arr, n) {
    const len = arr.length;
    // Handle cases where n > array length
    n = n % len;
    
    // Left rotation: take elements from index n and append first n elements
    return [...arr.slice(n), ...arr.slice(0, n)];
}

const originalArray = [12, 6, 43, 5, 7, 2, 5];
const rotated = rotateArray(originalArray, 3);

console.log("Original:", originalArray);
console.log("Rotated by 3:", rotated);


Original: [12, 6, 43, 5, 7, 2, 5]
Rotated by 3: [5, 7, 2, 5, 12, 6, 43]


Method 3: Right Rotation

To rotate elements to the right instead of left:

function rotateRight(arr, n) {
    const len = arr.length;
    n = n % len;
    
    // Right rotation: take last n elements and prepend them
    return [...arr.slice(-n), ...arr.slice(0, -n)];
}

const numbers = [1, 2, 3, 4, 5];
const rightRotated = rotateRight(numbers, 2);

console.log("Original:", numbers);
console.log("Right rotated by 2:", rightRotated);


Original: [1, 2, 3, 4, 5]
Right rotated by 2: [4, 5, 1, 2, 3]


Comparison

Conclusion

The slice and spread method is most efficient and doesn't modify the original array. Use prototype extension only when you need in-place rotation and don't mind slower performance.