Is there to check if a js variable is a d3 selection?

Question

I some variables coming into my function.

If the first of these is a d3 selection I want to use it, otherwise I want to use a default selection.

How do I check if a variable is a d3 selection or not?

Answer 1

To check if variable sel is a d3.selection:

var isselection = sel instanceof d3.selection;