From 2628189ece421579bc3dfedb2e11e5fb766fd675 Mon Sep 17 00:00:00 2001
From: Oleksii Trekhleb <trehleb@gmail.com>
Date: Wed, 29 Jan 2020 06:52:14 +0100
Subject: [PATCH] Add more principles.

---
 README.md | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 36cd902..4e96f60 100644
--- a/README.md
+++ b/README.md
@@ -217,12 +217,16 @@ const guessWhatAgain = sum({}, []); // -> 0
 _Bad 👎🏻_
 
 ```javascript
-function sum(a: number, b: number): number {
+function sum(a: number, b: number): ?number {
+  // Covering the case when we don't do transpilation and/or Flow type checks in JS.
+  if (typeof a !== 'number' && typeof b !== 'number') {
+    return undefined;
+  }
   return a + b;
 }
 
-// This one fails during the transpilation/compilation.
-const guessWhat = sum([], {});
+// This one should fails during the transpilation/compilation.
+const guessWhat = sum([], {}); // -> undefined
 ```
 
 ### 💩 You need to have an unreachable piece of code