Chunky.js

function chunkArrayInGroups(arr, size) {
  var chunky = [];
  
  var arraySize = arr.length;
  
  for(var i = 0; i < arraySize; i+= size) {
    chunky.push(arr.slice(i, i+size));
  }
  
  
  return chunky;
}

chunkArrayInGroups(  ["a", "b", "c", "d"], 2  );