Group buckets by date

groupByDate.js

/**
 * @function groupBucketsByDate
 * @desc This takes an array of objects and a date key to group off of.
 * It then will group all of the objects by that date key and will a distinct list
 * of dates and an array of counts for each date
 * @param {Object[]} buckets - An array of date buckets/objects
 * @param {string} key - The key to group the items off of
 * @param {Object} buckets[].bucket - A single date bucket in the array
 * @param {number} bucket.doc_count - The count of items for this particular bucket
 * @example const groups = groupBucketsByDate(buckets, 'key_as_string');
 * @return {Object} A list of values and counts that can be summed
 */
const groupBucketsByDate = (buckets, key) => {
  return buckets.reduce((groups, bucket) => {
    const date = bucket[key];
    const bucketCount = (bucket.doc_count || 0);
    const count = parseInt(groups[date] || 0);
    groups[date] = bucketCount + count;
    return groups;
  }, {});
}

/**
 * @function groupBucketsByDateToArray
 * @description Same as above, just returns an array of objects
 * @example const groups = groupBucketsByDate(buckets, 'key_as_string');
 * @param buckets 
 * @param key 
 * @returns {Object[]} An array of dates and count objects 
 */
const groupBucketsByDateToArray = (buckets, key) => {
  return buckets.reduce((groups, bucket) => {
    const date = bucket[key];
    const count = (bucket.doc_count || 0);
    const group = groups.find(g => g.date === date);
    
    if (group) {
      group.count += count;
      return groups;
    }
    
    grouped.push({ date: date, count: count });
    return groups;
  }, []);
}
const buckets = [
  { "key_as_string": "2038-01-01", "key": 2145916800000, "doc_count": 2032 },
  { "key_as_string": "2018-08-01", "key": 1533081600000, "doc_count": 23 },
  { "key_as_string": "2018-08-01", "key": 1533081600000, "doc_count": 23 }
];


console.log(groupBucketsByDate(buckets, 'key_as_string'));
console.log(groupBucketsByDateToArray(buckets, 'key_as_string'));