Why is there a 'null' value in JavaScript?

> I think that your conclusion that JavaScript defines undefined as "there is no such property" and null as "the property has no value" is perfectly correct.

This answers a puzzling irk I had with TypeScript where name?: <type> could have a valid value of <type> or undefined rather than what I'd expect to be null or a non-null valid value of <type>. If I consider that 'name' is a property of the containing object then undefined makes sense in context. It is annoying to say <type> | null | undefined though.