Is it possible to delete a variable declared using const?
delete is used to delete properties from an object.
delete foo;
will try to delete the property foo from the global object. Declared variables can never be removed with delete (no matter if you use const, let or var), and there is no other way to remove a "variable" (binding) (see @T.J.'s comment for some more details).
Related: How to unset a JavaScript variable?