Add comments to sorting.service

src/app/services/sorting.service.ts

@@ -1,17 +1,38 @@
 import {Priority} from './backend.service';
 
+/**
+ * Sort an array in place by a number associated with that item.
+ * @param items The items to sort.
+ * @param key Returns the number associated with an item.
+ */
 export function sortByNumberAscending<T>(items: T[], key: (T) => number) {
   return items.sort((a, b) => key(a) - key(b));
 }
 
+/**
+ * Sort an array in place by a string associated with that item.
+ * Strings will be sorted in alphabetic order.
+ * @param items The items to sort.
+ * @param key Returns the string associated with an item.
+ */
 export function sortByStringAscending<T>(items: T[], key: (T) => string) {
   return items.sort((a, b) => key(a).localeCompare(key(b)));
 }
 
+/**
+ * Sort an array in place by a date associated with that item.
+ * Dates will be sorted from old to new.
+ * @param items The items to sort.
+ * @param key Returns the date associated with an item.
+ */
 export function sortByDateAscending<T>(items: T[], key: (T) => Date) {
-  return items.sort((a, b) =>  <any>key(b) - <any>key(a));
+  return items.sort((a, b) =>  (key(b) as any) - (key(a) as any));
 }
 
+/**
+ * Converts a priority enum member to a number.
+ * @returns high -> 2, medium -> 1, low -> 0
+ */
 export function getNumberForPriority(priority: Priority): number {
   switch (priority) {
     case Priority.High:
@@ -21,4 +42,4 @@ export function getNumberForPriority(priority: Priority): number {
     case Priority.Low:
       return 0;
   }
-};
+}