Q114- Rotate an array forward by N steps in JavaScript

Rotating an array forward by N steps means moving the last N elements to the front while shifting the rest to the right.

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1️⃣ Using unshift and pop

function rotateArray(arr, n) {
  const len = arr.length;
  n = n % len; // handle n > arr.length

  for (let i = 0; i < n; i++) {
    const last = arr.pop(); // remove last element
    arr.unshift(last);      // add it to the front
  }
  return arr;
}

// Example
const arr = [1, 2, 3, 4, 5];
console.log(rotateArray(arr, 2)); // [4, 5, 1, 2, 3]

Explanation:

• pop() removes the last element
• unshift() adds it to the front
• Repeat n times to rotate

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2️⃣ Using Slice and Spread Operator (More Efficient)

function rotateArray(arr, n) {
  const len = arr.length;
  n = n % len; // handle n > arr.length
  return [...arr.slice(-n), ...arr.slice(0, len - n)];
}

// Example
const arr = [1, 2, 3, 4, 5];
console.log(rotateArray(arr, 2)); // [4, 5, 1, 2, 3]

Explanation:

• arr.slice(-n) → takes the last N elements
• arr.slice(0, len - n) → takes the first elements
• Spread operator combines them → rotated array

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⚡ Key Points:

• Always use n % arr.length to handle rotations greater than array length
• unshift/pop modifies the original array
• slice/spread returns a new array without mutation