refactor post model

src/utils/groupByAndMap.ts

@@ -0,0 +1,19 @@
+export function groupByAndMap<T, U>(
+  items: T[],
+  groupBy: (item: T) => string,
+  map: (item: T) => U,
+): Record<string, U[]> {
+  const groupings: Record<string, U[]> = {}
+
+  for (const item of items) {
+    const key = groupBy(item)
+
+    if (!groupings[key]) {
+      groupings[key] = []
+    }
+
+    groupings[key].push(map(item))
+  }
+
+  return groupings
+}