How can I skip key in object loop
<p>I was wondering if there is any way to skip key in object loop. If I have:</p>

<pre><code>obj = {
   key1 : [ 1, 2, 3 ],
   key2 : [ 4, 5 ],
   key3 : []
}
</code></pre>

<p>how can I skip, for example, the empty one. Because I want to <code>join()</code> the not empty arrays in that object, and filter them. If I join that empty array the filter looks for empty string and of course it doesn't find it, and everything brakes.</p>

<pre><code>var match = $('.widget');
for ( var i in obj ){
    var joined = obj[i].join();
    match = match.filter(joined);
}
</code></pre>

<p>I have tried to delete it:</p>

<pre><code>if ( obj[i].length == 0 ) {
    delete obj[i]
};
</code></pre>

<p>but error occurs that obj[i] is undefined and can't join it. How can I just skip it.</p>
