ArrayManipulator

function manipulator(manArr, commands) {
    for (let element of commands) {
        element = element.split(` `);
        let command = element.shift();
        if (command === `add`){
            manArr.splice(element[0], 0, Number(element[1]))
        } else if (command === `addMany`) {
            let index1 = element.shift();
            element.reverse();
            element.forEach(num => {
                manArr.splice(index1, 0, Number(num));
            });
        } else if (command === `contains`) {
            console.log(manArr.indexOf(Number(element[0])))
        } else if (command === `remove`){
            manArr.splice(Number(element[0]), 1);
        } else if (command === `shift`){
            for (let i = 0; i < element[0]; i++) {
                let firstEl = manArr.shift();
                manArr.push(firstEl);
            }
        } else if (command === `sumPairs`) {
            let newArr = [];
            for (let i = 0; i < manArr.length; i += 2) {
                let sum = manArr[i] + (manArr[i+1] || 0);
                newArr.push(sum);
            }
            manArr = newArr;
        } else if (command === `print`) {
            break;
        }
    }
    console.log('[ ' + manArr.join(', ') + ' ]')
}