What values will return 0 in this function?
<p>The following function uses a <a href="http://www.openjs.com/articles/syntax/short_circuit_operators.php" rel="nofollow">Short Circuit Operator</a> to return <code>0</code> as default:</p>

<pre><code>function custNumParse(str){
    return str*1||0;
}
</code></pre>

<p>I am not sure when this will return the second (I mean, I know that it will when <code>str*1</code> can't be evaluated to <code>true</code>), but I am not sure what inputs could produce that output when multiplying by <code>1</code>.</p>

<p>I know that the falsish values are <code>0, "", false, null, undefined, NaN</code>, but this doesn't help me that much.</p>

<p>In other words I am clueless what would happen when I use that function with objects or booleans, etc. I know I can test them all, but I am sure there is an easier way to go</p>

<p>Any ideas on what is the most proper way to find these guys without testing them all?</p>
