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Mar 17, 2017
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Update object-literal.md #146

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kikorb Mar 17, 2017
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26 changes: 24 additions & 2 deletions chapters/classes_and_objects/object-literal.md
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Expand Up @@ -20,7 +20,29 @@ window.MY_NAMESPACE ?= {}
This is equivalent to the following JavaScript:

{% highlight javascript %}
window.MY_NAMESPACE = window.MY_NAMESPACE || {};
if(window.MY_NAMESPACE === null || window.MY_NAMESPACE === undefined) {
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.
## Problem

You want to make a conditonal assignment if it does not exists or if it is falsy (empty, 0, null, false)

## Solution

Use the Conditional assignment operator

{% highlight coffeescript %}
window.my_variable ||= {}
{% endhighlight %}

## Discussion

This is equivalent to the following JavaScript:

{% highlight javascript %}
window.my_variable = window.my_variable || {};
{% endhighlight %}

Common JavaScript technique, using conditional assignment to ensure that we have an object that is not falsy