How do you verify that an integer is nan in javascript?

I've tried it only in firefox's javascript console but neither of the following statements return true

parseFloat('geoff') == NaN;

parseFloat('geoff') == Number.NaN;

Try this code.

isNaN(parseFloat("geoff"))

For checking whether any value is NaN, instead of just numbers, see here: How do you test for NaN in Javascript?