new recipe: create object literal if it does not exist

Author: Jesse House

chapters/objects/create-object-literal-if-not-exist.textile

@@ -0,0 +1,29 @@
+---
+layout: recipe
+title: Create an object literal if it does not already exist
+chapter: Objects
+---
+
+h2. Problem
+
+You want to initialize an object literal, but you do not want to overwrite the object if it already exists.
+
+
+h2. Solution
+
+Use the Existential operator
+
+{% highlight coffeescript %}
+window.MY_NAMESPACE ?= {} 
+{% endhighlight %}
+
+
+h2. Discussion
+
+This is equivalent to the following JavaScript:
+
+{% highlight javascript %}
+window.MY_NAMESPACE = window.MY_NAMESPACE || {};
+{% endhighlight %}
+
+Common JavaScript technique, using object literal to define a namespace. This saves us from clobbering the namespace if it already exists.