Get n numbers from array starting from given point JavaScript

We need to create a custom Array method that extracts n elements from an array starting at a given index, moving in a specified direction (left or right). When we reach array boundaries, the function wraps around to continue from the other end.

Problem Requirements

The function should take three parameters:

• n - number of elements to extract
• m - starting index (must be ? array.length - 1)
• direction - either 'left' or 'right'

For example, if we have [0, 1, 2, 3, 4, 5, 6, 7] and call get(4, 6, 'right'), it should return [6, 7, 0, 1] by wrapping around when it reaches the end.

Implementation

const arr = [0, 1, 2, 3, 4, 5, 6, 7];

Array.prototype.get = function(num, ind, direction) {
    const amount = direction === 'left' ? -1 : 1;
    
    if (ind > this.length - 1) {
        return false;
    }
    
    const res = [];
    for (let i = ind, j = 0; j < num; i += amount, j++) {
        if (i > this.length - 1) {
            i = i % this.length;
        }
        if (i < 0) {
            i = this.length - 1;
        }
        res.push(this[i]);
    }
    return res;
};

console.log("Moving right from index 6:", arr.get(4, 6, 'right'));
console.log("Moving left from index 6:", arr.get(9, 6, 'left'));

Moving right from index 6: [ 6, 7, 0, 1 ]
Moving left from index 6: [
  6, 5, 4, 3, 2,
  1, 0, 7, 6
]

How It Works

The function uses a direction multiplier (amount) to determine movement: -1 for left, +1 for right. When the index goes beyond array bounds, it wraps around using modulo for forward movement or resets to the last index for backward movement.

Example Breakdown

const testArr = [0, 1, 2, 3, 4, 5, 6, 7];

// Right direction: starts at index 6, gets 4 elements
console.log("Right from 6:", testArr.get(4, 6, 'right'));
// [6, 7, 0, 1] - wraps to beginning after reaching end

// Left direction: starts at index 3, gets 5 elements  
console.log("Left from 3:", testArr.get(5, 3, 'left'));
// [3, 2, 1, 0, 7] - wraps to end after reaching beginning

Right from 6: [ 6, 7, 0, 1 ]
Left from 3: [ 3, 2, 1, 0, 7 ]

Conclusion

This custom Array method enables circular extraction of elements in both directions. The wrapping behavior makes it useful for scenarios requiring continuous data access beyond array boundaries.