What does the double exclamation !! operator mean? [duplicate]
The !! ensures the resulting type is a boolean (true or false).
javascript:alert("foo") --> foo
javascript:alert(!"foo") --> false
javascript:alert(!!"foo") --> true
javascript:alert(!!null) --> false
They do this to make sure $('row') isn't null.
It's shorter to type than $('row') != null ? true : false.