[fendy3002]

Nice catch. Rather than date the author should've pass the DEBUG constant instead.

Or a function that return new date, but it'll make things complicated.

[mjbrusso]

However , to pass a constant I could use default parameter value.

[fendy3002]

It's the function definition that's responsible for defining default parameter.

It's the function caller that's responsible for that parameter with partial application / currying / closure.

It doesn't matter if you develop both, but if you use a library you'll need partial application to define default parameter.