function arrayManipulator(numbers, commands) {

    for (let command of commands) {
        let tokens = command.split(" ");
        let currentCommand = tokens[0];
        if (currentCommand === "add") {
            let index = Number(tokens[1]);
            let element = Number(tokens[2]);
            numbers.splice(index, 0, element);
        } else if (currentCommand === "addMany") {
            let index = Number(tokens[1]);
            let setOfElements = tokens.slice(2, tokens.length);
            numbers.splice(index, 0, ...setOfElements);

        } else if (currentCommand === "contains") {
            let result = numbers.indexOf(+tokens[1])
            console.log(result);
        } else if (currentCommand === "remove") {
            let index = Number(tokens[1]);
            numbers.splice(index, 1)

        } else if (currentCommand === "shift") {
            let positions = Number(tokens[1]);
            for (let i = 0; i < positions; i++) {
                let first = numbers.shift();
                numbers.push(first);
            }
        } else if (currentCommand === "sumPairs") {
            let resultArr = [];
            if (numbers.length % 2 !== 0) {
                numbers.push(0);
            }
            for (let i = 0; i < numbers.length - 1; i += 2) {
                let sum = numbers[i] + numbers[i + 1];
                resultArr.push(sum)
            }
            numbers = resultArr;
        } else if (currentCommand === "print") {
            console.log(`[ ${numbers.map(Number).join(", ")} ]`);

        }

    }
    //console.log(`[ ${numbers.map(Number).join(", ")} ]`);

}
arrayManipulator(
    [1, 2, 4, 5, 6, 7],
    ['add 1 8', 'contains 1', 'contains 3', 'print'])

// 0
// -1
// [ 1, 8, 2, 4, 5, 6, 7 ]

// arrayManipulator([1, 2, 3, 4, 5],
//     ['addMany 5 9 8 7 6 5', 'contains 15', 'remove 3', 'shift 1', 'print'])

// -1
// [ 2, 3, 5, 9, 8, 7, 6, 5, 1 ]