type-alias.md

Type Alias

A type alias is a type that:

• has its own name,
• and reuses the definition of an existing type

For example:

type MediaTypeOptions = OnErrorOptions;

With careful use, they bring important benefits.

• They're often used as a form of documentation, or as an opportunity to write documentation. That's definitely a good thing. We don't believe that code is documentation.
• They provide a level of future-proofing. As long as developers use them, we can add more fields to MediaTypeOptions without accidentally changing the options to any other functions.
• But they don't provide two-way isolation. MediaTypeOptions will automatically gain any new fields that we add to OnErrorOptions. That may be an unintended side effect.