What is the syntax to declare Nested Namespace in TypeScript?

In TypeScript, declaring nested namespaces is typically achieved by defining one or more namespaces within another namespace. Here is a simple example demonstrating how to declare nested namespaces in TypeScript:

typescript
namespace OuterNamespace {
    export namespace InnerNamespace {
        export function display() {
            console.log("Hello from InnerNamespace");
        }
    }

    export function display() {
        console.log("Hello from OuterNamespace");
    }
}

// Using functions from nested namespaces
OuterNamespace.InnerNamespace.display();  // Output: Hello from InnerNamespace
OuterNamespace.display();                 // Output: Hello from OuterNamespace

In this example, OuterNamespace is an outer namespace, and InnerNamespace is a nested namespace defined within OuterNamespace. A display function is defined within InnerNamespace, and similarly, a display function is defined within OuterNamespace. They can be accessed and called using the namespace name followed by a dot.

Note that if you want to call a function or variable within a namespace from outside the namespace, you need to use the export keyword to export them, as shown in the example above.

Nested namespaces are well-suited for organizing code, grouping related functionalities and components together, while also avoiding pollution of the global namespace.