rewrite expand function

internal/statsapi/feed.go

@@ -36,6 +36,12 @@ type about struct {
 	CaptivatingIndex json.Number
 }
 
+func expand(arr []any, idx int) []any {
+	front := append(arr[:idx], nil)
+	all := append(front, arr[idx:])
+	return all
+}
+
 func setValue(obj any, key string, value any) error {
 	var err error
 	switch v := obj.(type) {
@@ -51,13 +57,7 @@ func setValue(obj any, key string, value any) error {
 			break
 		}
 
-		if len(v) <= idx {
+		v = expand(v, idx)
-			arr := make([]any, idx+1)
-			for i, val := range v {
-				arr[i] = val
-			}
-			v = arr
-		}
 		v[idx] = value
 	default:
 		err = errors.New("couldn't determine type")
@@ -66,16 +66,6 @@ func setValue(obj any, key string, value any) error {
 	return err
 }
 
-func expand(v []any, idx int) {
-	if len(v) <= idx {
-		arr := make([]any, idx+1)
-		for i, val := range v {
-			arr[i] = val
-		}
-		v = arr
-	}
-}
-
 func patch(obj any, path string, value any) error {
 	var err error
 	first, rest, found := strings.Cut(path, "/")
@@ -94,7 +84,7 @@ func patch(obj any, path string, value any) error {
 			break
 		}
 
-		expand(v, idx)
+		v = expand(v, idx)
 		err = patch(v[idx], rest, value)
 	default:
 		err = errors.New("couldn't determine type")