javascript for-in loop in an Array
<p>If the code is this:</p>

<pre><code>arr=Array("a","b","c");
for(i in arr);
{
 alert(i);
}
</code></pre>

<p>there is no any alert,but if it is this:</p>

<pre><code>arr=new Array("a","b","c");
for(i in arr)
{
 alert(i);//alerts 0,1,2
}
</code></pre>

<p>What is the reason?</p>
