fix: Use Promise.all in toJSON iteration. (#1077)

* fix: Use Promise.all in toJSON iteration.

* Only normalize the hint once.

packages/orm/src/json.ts

@@ -107,18 +107,21 @@ export async function toJSON<T extends Entity, const H extends JsonHint<T>>(
   const entity = Array.isArray(entityOrList) ? entityOrList[0] : entityOrList;
   const loadHint = convertToLoadHint(getMetadata(entity), hint as any, true);
   await entity.em.populate(entityOrList, loadHint);
+  const normHint = normalizeHint(hint as any);
 
   if (Array.isArray(entityOrList)) {
-    const list = [];
-    for (const entity of entityOrList) {
-      const json = {};
-      await copyToPayload(json, entity, normalizeHint(hint as any));
-      list.push(json);
-    }
-    return list as any;
+    const list = [] as any;
+    await Promise.all(
+      entityOrList.map((entity) => {
+        const json = {};
+        list.push(json);
+        return copyToPayload(json, entity, normHint);
+      }),
+    );
+    return list;
   } else {
     const json = {};
-    await copyToPayload(json, entity, normalizeHint(hint as any));
+    await copyToPayload(json, entity, normHint);
     return json as any;
   }
 }