Fix group performance: don't reduce + spread (#169)

Co-authored-by: Ray Epps <[email protected]>

Author: sodiray

Diff for: cdn/radash.esm.js

@@ -1,8 +1,10 @@
 const group = (array, getGroupId) => {
   return array.reduce((acc, item) => {
     const groupId = getGroupId(item);
-    const groupList = acc[groupId] ?? [];
-    return { ...acc, [groupId]: [...groupList, item] };
+    if (!acc[groupId])
+      acc[groupId] = [];
+    acc[groupId].push(item);
+    return acc;
   }, {});
 };
 const boil = (array, compareFunc) => {

Diff for: cdn/radash.js

@@ -4,8 +4,10 @@ var radash = (function (exports) {
   const group = (array, getGroupId) => {
     return array.reduce((acc, item) => {
       const groupId = getGroupId(item);
-      const groupList = acc[groupId] ?? [];
-      return { ...acc, [groupId]: [...groupList, item] };
+      if (!acc[groupId])
+        acc[groupId] = [];
+      acc[groupId].push(item);
+      return acc;
     }, {});
   };
   const boil = (array, compareFunc) => {