Update groupAndSum.js

Documented

groupAndSum.js

@@ -1,19 +1,62 @@
-// Author Tony Germano 
-// Discusion orginated on Mirth Slack from discussion started by nafwa03
+/**
+ * Author Tony Germano
+ * Discussion originated on Mirth Slack from discussion started by nafwa03
+ */
 
+/**
+ * Groups and sums the elements of an array of objects based on the specified groupByKeys and sumKeys.
+ * This function takes an array of objects (arr), and groups them based on the specified groupByKeys. 
+ * It then sums the values of sumKeys for each group. The resulting array of objects is returned after
+ * the grouping and summing.
+ *
+ * @param {Array<Object>} arr - The array of objects to be grouped and summed.
+ * @param {Array<string>} groupByKeys - The object keys used for grouping.
+ * @param {Array<string>} sumKeys - The object keys used for summing.
+ * @returns {Array<Object>} The resulting array of objects after grouping and summing.
+ *
+ * @example
+ * const inputArray = [
+ *   { category: 'A', subcategory: 'X', value: 10 },
+ *   { category: 'A', subcategory: 'Y', value: 15 },
+ *   { category: 'A', subcategory: 'X', value: 5 },
+ *   { category: 'B', subcategory: 'X', value: 20 }
+ * ]
+ *
+ * const groupedAndSummed = groupAndSum(inputArray, ['category', 'subcategory'], ['value'])
+ *
+ * // Result:
+ * // [
+ * //   { category: 'A', subcategory: 'X', value: 15 },
+ * //   { category: 'A', subcategory: 'Y', value: 15 },
+ * //   { category: 'B', subcategory: 'X', value: 20 }
+ * // ]
+ */
 function groupAndSum(arr, groupByKeys, sumKeys) {
+  // Function to create a key for grouping based on the groupByKeys
   const toGroupKey = o => groupByKeys.map(k => o[k]).join('|')
+
+  // Function to create a new result object based on the sourceObj and the required keys
   const newResultObject = sourceObj => groupByKeys
     .map(k => [k, sourceObj[k]])
     .concat(sumKeys.map(k => [k, 0]))
     .reduce((targetObj, [k, v]) => (targetObj[k] = v, targetObj), {})
-​
-  const groupMap = Object.create(null)
+
+  // Create an empty groupMap to store the grouped objects
+  const groupMap = {}
+
+  // Reduce the input array to a new array with grouped and summed objects
   return arr.reduce((result, currentObject) => {
     const key = toGroupKey(currentObject)
+
+    // Function to push a new result object into the result array and set its value in the groupMap
     const pushSetAndGet = o => (result.push(o), groupMap[key] = o)
+
+    // Get the result object from the groupMap, or create a new one and add it to the result array
     const resultObject = groupMap[key] || pushSetAndGet(newResultObject(currentObject))
+
+    // Sum the values of the sumKeys in the result object
     sumKeys.forEach(k => { resultObject[k] += currentObject[k] || 0 })
+
     return result
   }, [])
 }