[guide] [react] add a note preferring normal functions for functional stateless components.

react/README.md

@@ -47,7 +47,7 @@
     }
     ```
 
-    And if you don't have state or refs, prefer functions over classes:
+    And if you don't have state or refs, prefer normal functions (not arrow functions) over classes:
 
     ```javascript
 
@@ -58,6 +58,11 @@
       }
     }
 
+    // bad (since arrow functions do not have a "name" property)
+    const Listing = ({ hello }) => (
+      <div>{hello}</div>
+    );
+
     // good
     function Listing({ hello }) {
       return <div>{hello}</div>;