Vertex

Structural typing and assignability

TypeScript compares shapes, not names. Two unrelated types are interchangeable if their members line up, which explains most surprising assignability errors.

Lesson 1.111m 49sIntermediate22.1k students

Lesson length

11:49

What this lesson covers

  • Compare types by structure rather than declaration
  • Read an assignability error from the mismatched member up
  • Use branded types when structural compatibility is too loose

This lesson sits in How the Type System Thinks, part of TypeScript for Application Developers. It assumes what came before it and leads directly into the next lesson in the module.

In this lesson you will

  • Compare types by structure rather than declaration
  • Read an assignability error from the mismatched member up
  • Use branded types when structural compatibility is too loose

Resources

Next lessonUnions and narrowing1.2 · 10m 20s