From 53c59b0aedfda3f686154e9c35cb8717225a10a1 Mon Sep 17 00:00:00 2001
From: Andrea Giammarchi <andrea.giammarchi@gmail.com>
Date: Mon, 25 May 2020 17:32:21 +0200
Subject: [PATCH] Avoid unnecesary prototype loop

## Background

People at redux-toolkit copy/pasted this utility in there, and [they are not welcoming a PR](https://github.com/reduxjs/redux-toolkit/pull/581) because of that, but the `while` loop in here is completely unnecessary, as the comparison is made on the first `proto` only.

## Improvements

  * _O(1)_ instead of _O(n)_
  * safe fallback for `Object.create(null)` cases
  * fast lane for `new Class()` derived objects
  * better performance
  * smaller code size

As this change has zero downsides, unless I am missing some explicit reason to `while` loop instead of never using `getPrototypeOf` more than twice, I hope it'll get in, so that others might copy and paste this new version.

Best Regards.
---
 src/utils/isPlainObject.ts | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/src/utils/isPlainObject.ts b/src/utils/isPlainObject.ts
index 9d1956328a..fc7ac3ab5e 100644
--- a/src/utils/isPlainObject.ts
+++ b/src/utils/isPlainObject.ts
@@ -3,12 +3,9 @@
  * @returns True if the argument appears to be a plain object.
  */
 export default function isPlainObject(obj: any): boolean {
-  if (typeof obj !== 'object' || obj === null) return false
-
-  let proto = obj
-  while (Object.getPrototypeOf(proto) !== null) {
-    proto = Object.getPrototypeOf(proto)
-  }
-
-  return Object.getPrototypeOf(obj) === proto
+  return (
+    typeof value === 'object' &&
+    value !== null &&
+    Object.getPrototypeOf(Object.getPrototypeOf(value) || {}) === null
+  )
 }