Nested namespace

Learn nested namespaces.

Nested namespaces

Namespaces can be nested. With namespace Outer { export namespace Inner { ... } } you can export one namespace inside another. Members are accessed from outside as Outer.Inner.member via a dot chain.

namespace Dis {
  export namespace Ic {
    export function f() {
      return "iç";
    }
  }
}
console.log(Dis.Ic.f());  // "iç"

Each level must be exported

In nested namespaces, both the outer and inner namespace must be marked export to be accessible from outside. Otherwise the inner namespace is invisible from outside and the Outer.Inner.member access is a compile error.

Exercise Apply the nested pattern

The compiled equivalent of a nested namespace structure can be expressed as a nested object pattern. Define an object Dis with an inner object Ic. Inside Ic, place a method f(): string with body return "iç". Call it from outside via the dot chain and print the result with console.log.

Show example solution

const Dis = {
  Ic: {
    f(): string {
      return "iç";
    }
  }
};
console.log(Dis.Ic.f());

Test yourself

How is a member in a nested namespace accessed?
- Via import Ic from Dis
- Only as Ic.member
- As Dis::Ic::member
- Via the Dis.Ic.member dot chain
Show answer

Via the Dis.Ic.member dot chain — In a nested namespace, a member is accessed via the Dis.Ic.member dot chain. Ic.member alone does not work because Ic is not directly visible from outside; :: is C++ syntax; import is for module imports.

Access the inner namespace

namespace Dis {
  export namespace Ic {
    export function f(): string {
      return "iç";
    }
  }
}
console.log(Dis.____.f());

Show answer

namespace Dis {
  export namespace Ic {
    export function f(): string {
      return "iç";
    }
  }
}
console.log(Dis.Ic.f());

Nested namespace parts

export namespace Ic

Inner namespace export
namespace Dis

Outer namespace declaration
Dis.Ic.f()

Call via dot chain
her seviye export

Visibility rule for nesting

Next lesson: Namespace vs module

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