Summary - Type alias

Write a configuration type with aliases.

Summary - Type alias

Type aliases provide reuse by naming types, create new types with unions, and are more general than interfaces. Together they enable flexible and modular type definitions.

type Deger = number | string;
type Ayar = { ad: string; deger: Deger };

These features together create powerful configuration types.

Exercise Write a configuration type

Define a type alias named Deger (number | string union). Define a type alias named Ayar ({ ad: string; deger: Deger }). Declare a variable named ayar of type Ayar with value { ad: "timeout", deger: 30 }. Print the value of ayar.ad with console.log.

Show example solution

type Deger = number | string;
type Ayar = { ad: string; deger: Deger };
let ayar: Ayar = { ad: "timeout", deger: 30 };
console.log(ayar.ad);

Test yourself

What does using another alias in an alias definition enable?
- Building complex types from simple ones
- Faster execution
- Less memory usage
- Types becoming immutable
Show answer

Building complex types from simple ones — Aliases can reference other aliases; this enables building complex types modularly from simpler parts.

Complete the configuration value type

type Ayar = {
  ad: string;
  deger: ____;
};

Show answer

type Ayar = {
  ad: string;
  deger: number | string;
};

Type alias summary

type ID = number

Primitive type naming
type X = A | B

Type union
type vs interface

Type is more general
Type alias

Naming a type

Next lesson: Union types

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