Undefined Vs. Undeclared Variables
Definition of UNDECLARED: There was no preceding var or global statement, and no statement that explicitly or implicitly assigns a value to the variable.
Definition of DECLARED BUT UNDEFINED: There was a preceding var statement, but no value was assigned to the variable in the var statement or subsequently.
The best I've found so far is:
This test distinguishes between defined and undefined variables, but does not distinguish between "undefined" and "defined but undeclared." Can you help?