added facade pattern

Author: AnjanishKumar

pattern/facade-pattern.js

@@ -0,0 +1,50 @@
+// a simple facade that masks the various browser-specific methods
+var window = window || null;
+
+function addEvent( element, event, callback ) {
+  
+  if( window.addEventListener ) {
+    element.addEventListener( event, callback, false );
+  } else if( document.attachEvent ) {
+    element.attachEvent( 'on' + event, callback );
+  } else {
+    element[ 'on' + event ] = callback;
+  }
+  
+}
+
+// another example of a module which usages facade pattern to hide the direct access to 
+// internal method
+var MyModule = ( function( window, undefined ) {
+
+    
+    function someMethod() {
+      console.log( 'some method' );
+    }
+    
+    function someOtherMethod() {
+      console.log( 'some other method' );
+    }
+    
+    // expose publicly available methods
+    return {
+      
+      // in our normal revealing module pattern, we'd do the following:
+      someMethod : someMethod,
+      
+      // in the facade pattern, we mask the internals so no one has direct access by doing this:
+      someOtherMethodFacade : function() {
+        someOtherMethod();
+      }
+      
+    };
+    
+  
+  
+} )( window );
+
+//example usages
+
+MyModule.someMethod(); // logs "some method"
+MyModule.someOtherMethodFacade(); //logs "some other method"
+MyModule.someOtherMethod(); // throw error "MyModule.someOtherMethod is not a function"