difference between if (!!variable), and, if (variable)?
<p>Is there any difference (in JS) between using the double negative <code>!!</code> and not using it at all?</p>

<p>For example</p>

<p><code>if (!!variable){...</code>   vs. <code>if (variable){...</code></p>

<p>I know there are times where I've gotten a warning using the 2nd method..</p>

<p>When should each be used? and when will each throw a warning in the console? (for variables, objects, arrays etc.)</p>

<p>Thanks!!</p>
