leftRotationArray

function leftRotation(arr,rotation){
    rotation %= arr.length;
   while(rotation > 0){
     let firstEl = arr[0];
     for(let i = 0;i < arr.length;i++){
         arr[i] = arr[i + 1];
     }
        arr[arr.length-1] = firstEl;

     rotation--;
   }
   console.log(arr.join(', '));
}
 leftRotation([1,2,3,4],3);