text: 
  module.exports = function towelSort (matrix) {
    if(matrix == undefined) return [];
    let arr =[];
    for(let i = 0; i < matrix.length; i++){
  if(i % 2 == 0 ){
    arr=arr.concat(matrix[i]);
  } else {
  arr=arr.concat(matrix[i].reverse());
  }
  }
  return arr;
  }
  