JS: Added isset helper function

Signed-off-by: Elliot Condon <e@elliotcondon.com>
added missing 'var'

Signed-off-by: Elliot Condon <e@elliotcondon.com>
WYSIWYG Field: Major JS update + removed live functions

Signed-off-by: Elliot Condon <e@elliotcondon.com>