Describing objects with interfaces

An interface names the shape of an object: which properties it has and their types. Annotate a value with the interface and the compiler enforces the shape.

Worked example

How it reads

interface Cloud { ... } names a reusable object shape
isFluffy? marks the altitude-related field as optional

Cloud tip: Use optional properties with a question mark to allow fields to be omitted safely.

index.ts

TYPESCRIPT

type-checked, then run in your browser

Console

Run your code to see its output here.

YOUR TURN

Add an optional constellation?: string to Star, create deneb with the constellation "Cygnus", and log deneb.constellation.

Press Run to check your work.

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