update snippets 62-78

snippets/isBoolean.md

@@ -6,6 +6,9 @@ Use `typeof` to check if a value is classified as a boolean primitive.
 
 ```js
 const isBoolean = val => typeof val === 'boolean';
-// isBoolean(null) -> false
-// isBoolean(false) -> true
+```
+
+```js
+isBoolean(null) -> false
+isBoolean(false) -> true
 ```