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TypeScript in Depth · Interfaces & Types · Lesson 6 of 16

type Aliases vs Interfaces

Concept

type Aliases vs Interfaces

type can name any type, including unions, while interface is best for describing object shapes that might be extended later.

By the end of this lesson
  • Explain the core idea behind type Aliases vs Interfaces.
  • Predict output before running a change.
  • Test one realistic and one unusual input.
  • Use the result to make the next decision.
How to study this page
  1. 1. Read one concept.
  2. 2. Change the example.
  3. 3. Run, compare, and explain.
  4. 4. Complete the challenge below.
ExampleRunnable
type ID = string | number;
interface User {
  id: ID;
  name: string;
}
Try it Yourself »
Self-check before continuing

Without looking at the example, describe what changes when you modify one input in type Aliases vs Interfaces. Then reopen the editor and prove your explanation with a small test.

You are ready to continue when you can predict, test, and explain the result.

Your turn

Create a type alias for a Status that can be "active" or "inactive".

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Console

Output will appear here...