splitArray.js

function splitArray(arr, k) {
  const length = arr.length;
  const middle = Math.floor(length / k);
  const left = arr.slice(middle * k, length);
  let result = [], cursor = 0;
  
  while(cursor < middle) {
    result.push(arr.slice(cursor * k, cursor * k + k))
    cursor++;
  }

  if (left.length === 0) {
    return result;
  }
  
  return result.concat([left]);
}