function chunkArrayInGroups(arr, size) {
  // Break it up.
    var newArr = [];
    var j = 0;

for (var i=0; i < arr.length; i+= size) {
    var smallArray = arr.slice(i,i+size);
    newArr.push(smallArray.concat());

}


  return newArr;
}

chunkArrayInGroups(["a", "b", "c", "d"], 3);