refactor: make isPlainObject logic more readable

Author: pi0

src/_utils.ts

@@ -1,16 +1,22 @@
-// From sindresorhus/is-plain-obj
-// MIT License
+// Forked from sindresorhus/is-plain-obj (MIT)
 // Copyright (c) Sindre Sorhus <sindresorhus@gmail.com> (https://sindresorhus.com)
 export function isPlainObject(value: unknown): boolean {
   if (value === null || typeof value !== "object") {
     return false;
   }
   const prototype = Object.getPrototypeOf(value);
-  return (
-    (prototype === null ||
-      prototype === Object.prototype ||
-      Object.getPrototypeOf(prototype) === null) &&
-    !(Symbol.toStringTag in value) &&
-    !(Symbol.iterator in value)
-  );
+
+  if (
+    prototype !== null &&
+    prototype !== Object.prototype &&
+    Object.getPrototypeOf(prototype) !== null
+  ) {
+    return false;
+  }
+
+  if (Symbol.toStringTag in value || Symbol.iterator in value) {
+    return false;
+  }
+
+  return true;
 }