How do I check if a JavaScript parameter is a number?
<p>I'm doing some trouble-shooting and want to add a check that a parameter to a function is a number. How do I do this?</p>

<p>Something like this...</p>

<pre><code>function fn(id) {
    return // true iff id is a number else false
}
</code></pre>

<p>Even better is if I can check that the parameter is a number AND a valid integer.</p>
