Object returning NaN when sum values
<p>I'll admit I'm weak in JavaScript and JSON. I've spent a lot of time attempting to figure out why numbers from my objects returns NaN when they are added together. With that in mind, below is my JSON, stored to a variable:</p>

<pre><code>var data = [
    {
        "acc_ext_id": null,
        "cat_code": 10002,
        "cat_ds": "REVENUE",
        "category_id": null,
        "chart_id": null,
        "created_at": null,
        "dept_id": null,
        "feb": null,
        "id": null,
        "jan": 30,
        "note": null,
        "total_cost": null,
        "updated_at": null,
        "year_id": null
    },
    {
        "acc_ext_id": "41260-02600",
        "cat_code": 10002,
        "cat_ds": "REVENUE",
        "category_id": 2,
        "chart_id": 2373,
        "created_at": "2013-01-15 16:43:52.169213",
        "dept_id": 86,
        "feb": 45,
        "id": 3,
        "jan": 60,
        "note": "Two",
        "total_cost": 105,
        "updated_at": "2013-01-15 16:43:52.169213",
        "year_id": 1
    }
]
</code></pre>

<p>I then attempt to iterate over the objects and sum the values:</p>

<pre><code>var jan;

for (var i=0;i&lt;data.length;i++){ 
    if(data[i].jan != null){    
        jan += parseFloat(data[i].jan);
        console.log(jan);
    }
}
</code></pre>

<p>Printed out in the console is <code>NaN</code>.  I've attempted to parse the number as well as leave it raw, but to no avail.  Is there something wrong with my objects?  Here is a jsFiddle to illustrate: <a href="http://jsfiddle.net/5E2pm/3/" rel="nofollow">http://jsfiddle.net/5E2pm/3/</a></p>
