Regular Expression to check for Empty fields

[punterf16]

I need a regular expression to check for empty field within an input string...
i Tried working with a expression at http://www.tutorialspark.com/javascript/JavaScript_Regular_Expressions_MetaCharacters.php but its not working well please help

[Duthomhas]

How do you define "empty field"?

[edit]
If you are trying to parse a CSV or something, just check for some number of spaces surrounded by delimiters:

(^|,)\s*(,|$)