08. Array Manipulator

function arrayManipulator(arr, inputCommands) {

    let commands = inputCommands.shift().split(' ');

    while (commands[0] !== 'print') {
        let currCommand = commands[0];

        switch (currCommand) {
            case 'add': arr.splice(commands[1], 0, Number(commands[2]));
                break;
            case 'addMany':
                commands.shift();
                let elements = commands.map(Number);
                let index = elements.shift();
                addMany(index, elements, arr);
                break;
            case 'contains': console.log(contains(Number(commands[1])));
                break;
            case 'remove': arr.splice(Number(commands[1]), 1);
                break;
            case 'shift': arr = shift(Number(commands[1]), arr);
                break;
            case 'sumPairs':
                arr = sumPairs(arr);
                break;
        }

        commands = inputCommands.shift().split(' ')
    }
    console.log(`[ ${arr.join(', ')} ]`);

    function contains(trgNum) {
        let isFound = false;
        for (let i = 0; i < arr.length; i++) {
            if (arr[i] === Number(trgNum)) {
                isFound = true;
            }
        }
        if (isFound) {
            return 0;
        } else {
            return -1;
        }
    }

    function shift(rotations, array) {
        let realRotations = rotations % array.length;
        let result = [];

        for (let i = 0; i < array.length; i++) {
            let currentElement = array[i];

            if (i >= realRotations) {
                result.push(currentElement);
            }
        }

        for (let j = 0; j < array.length; j++) {
            let currentElement = array[j];

            if (j < realRotations) {
                result.push(currentElement);
            } else {
                break;
            }
        }

        return result;
    }

    function addMany(index, elements, arr) {
        for (let element of elements) {
            arr.splice(index, 0, element);
            index++;
        }
    }

    function sumPairs(array) {
        let result = [];

        for (let i = 0; i < array.length; i += 2) {
            let currentElement = array[i];
            let nextElement = array[i + 1];
            let currentSum = currentElement + nextElement;
            if (nextElement !== undefined) {
                result.push(currentSum);
            } else {
                result.push(currentElement);
            }
        }

        return result;
    }
}