Here's a ES6 version using reduce

const perChunk = 2 // items per chunk    

const inputArray = ['a','b','c','d','e']

const result = inputArray.reduce((resultArray, item, index) => { 
  const chunkIndex = Math.floor(index/perChunk)

  if(!resultArray[chunkIndex]) {
    resultArray[chunkIndex] = [] // start a new chunk
  }

  resultArray[chunkIndex].push(item)

  return resultArray
}, [])

console.log(result); // result: [['a','b'], ['c','d'], ['e']]

And you're ready to chain further map/reduce transformations. Your input array is left intact

If you prefer a shorter but less readable version, you can sprinkle some concat into the mix for the same end result:

inputArray.reduce((all,one,i) => {
   const ch = Math.floor(i/perChunk); 
   all[ch] = [].concat((all[ch]||[]),one); 
   return all
}, [])

You can use remainder operator to put consecutive items into different chunks:

const ch = (i % perChunk); 

Using generic groupBy function (taken from this lib):

const groupBy = (groupingFn, arr) => {
  const groups = {};

  arr.forEach((item) => {
    const key = groupingFn(item);

    if (groups[key] !== undefined) {
      groups[key].push(item);
    } else {
      groups[key] = [item];
    }
  });

  return groups;
};

const arr = [
  { id: 1, category: "category 1" },
  { id: 2, name: "category 2" },
  { id: 3, name: "category 1" },
  { id: 4, name: "category 3" }
];

const grouped = Object.values(
  groupBy((item) => item.name || item.category, arr)
);

console.log(grouped);