Validate that a string is a positive integer
<p>I would like the simplest, failsafe test to check that a string in JavaScript is a positive integer.</p>

<p><code>isNan(str)</code> returns true for all sorts of non-integer values and <code>parseInt(str)</code> is returning integers for float strings, like "2.5". And I don't want to have to use some jQuery plugin either.</p>
