63 -> 100

function solve(manipulatedArr, commandsArr) {

  for (let i = 0; i < commandsArr.length; i++) {
    let commandArr = commandsArr[i].split(' ');

    if (commandArr[0] == 'add') {
      manipulatedArr.splice(commandArr[1], 0, Number(commandArr[2]));
      // ====================================================
    } else if (commandArr[0] == 'addMany') {
      commandArr.shift();
      let index = commandArr.shift();

      for (let i = 0; i < commandArr.length; i++) {
        commandArr[i] = Number(commandArr[i]);
      }

      manipulatedArr.splice(index, 0, ...commandArr);
      // ====================================================
    } else if (commandArr[0] == 'contains') {
      if (manipulatedArr.includes(Number(commandArr[1]))) {
        console.log(manipulatedArr.indexOf(Number(commandArr[1])));
      } else {
        console.log(-1);
      }
      // ====================================================
    } else if (commandArr[0] == 'remove') {
      manipulatedArr.splice(commandArr[1], 1);
      // ====================================================
    } else if (commandArr[0] == 'shift') {
      for (let i = 0; i < commandArr[1]; i++) {
        let shiftedEl = manipulatedArr.shift();
        manipulatedArr.push(shiftedEl);
      }
      // ====================================================
    } else if (commandArr[0] == 'sumPairs') {
      let resultArr = [];
      for (let i = 0; i < manipulatedArr.length; i += 2) {
        let second = manipulatedArr[i + 1]
        if (second === undefined)
          second = 0
        let sum = manipulatedArr[i] + second;
        resultArr.push(sum);
      }
      manipulatedArr = resultArr;
      // ====================================================
    } else if (commandArr[0] == 'print') {
      manipulatedArr = manipulatedArr.join(', ');
      console.log(`[ ${manipulatedArr} ]`);
      break;
    }
  }
}