Stub typeof slide.

Author: RyanMcG

index.html

@@ -144,6 +144,13 @@
                 x // → undefined
                 var y = 10;
           </section>
+          <section data-markdown>
+            ## typeof
+
+                typeof x // → "undefined"
+                x // throws a reference error
+                var x;
+          </section>
           <section data-markdown>
             ## Why should I use var?
           </section>