In Rust you usually use either method chaining (CustomObject::new(param1, param2).option15('bar')) or the struct update syntax (CustomObject { param1: param1, param2: param2, option15: 'bar', ..DEFAULT_CUSTOM_OBJECT }) for this. No extra complexity of "zero values" necessary (and the concept of a zero value would be incoherent in Rust anyway).
But you have either the complexity of multiple closures, or complex mutability (side effects) with that strategy, depending on how you approach your implementation. In either case the outcome could be less than ideal, and have more chance of unexpected results.
Is this...
var obj = new CustomObject(...);
...
obj.option15('bar');
The same as
var obj = new CustomObject(...).option15('bar');
IE: does calling option15 create a new closure/space that is separate from the original object (more functional separation) or does it mutate the original object?
I tend to prefer to limit mutations as much as possible in my code... it really just depends on your needs.
