Array Manipulator

function solve(arr,commands){

    for(let i = 0; i < commands.length; i++){
        let splited = commands[i].split(' ');
        let command = splited[0];
            if(command === 'add'){
               add();
            }
            else if(command === 'addMany'){
               addMany();
            }
            else if(command === 'contains'){
               contains();
            }
            else if(command === 'remove'){
                remove();
             }
             else if(command === 'shift'){
                shift();
             }
             else if(command === 'sumPairs'){
                sumPairs();
             }
             else if(command === 'print'){
                print();
                break;
             }
            function add(){
                let index = parseInt(splited[1]);
                let element = parseInt(splited[2]);
                arr.splice(index,0,element);
            }
            function addMany(){
                let index = parseInt(splited[1]);
                for(let j = splited.length-1; j >= 2 ; j--){
                    let element = parseInt(splited[j]);
                    arr.splice(index,0,element);
                }
            }
            function contains(){
                let element = parseInt(splited[1]);
                    console.log(arr.indexOf(element));
           }
           function remove(){
                 let index = parseInt(splited[1]);
                 arr.splice(index,1);
           }
           function shift(){
                let position = parseInt(splited[1]);
                for(let a = 0; a < position; a++){
                    let first = arr.shift();
                    arr.push(first);
               }
           }
             function sumPairs(){
                arr = arr.map((e, i, arr) => i < arr.length - 1 ? (arr[i] += arr[i + 1]) : arr[i] = arr[i]).filter((e, i) => i % 2 === 0);
             }
             function print(){
                console.log(arr);
             }
    }
}