How to check 'undefined' value in jQuery

Question

Possible Duplicate:
Detecting an undefined object property in JavaScript
javascript undefined compare

H

Answer 1

In this case you can use a === undefined comparison: if(val === undefined)

This works because val always exists (it's a function argument).

If you wanted to test an arbitrary variable that is not an argument, i.e. might not be defined at all, you'd have to use if(typeof val === 'undefined') to avoid an exception in case val didn't exist.