How to fix Namespace declaration must have a name in TypeScript

First, examine your namespace declaration. A valid namespace declaration should look like this:

namespace MyNamespace {
  // Your code here
}

Make sure you have:
1. The namespace keyword
2. A valid name (identifier) after the keyword
3. Opening and closing braces {}
4. Proper indentation and formatting

Ensure your namespace name follows TypeScript identifier rules:
- Starts with a letter (a-z, A-Z) or underscore (_)
- Can contain letters, digits (0-9), or underscores
- Cannot be a TypeScript reserved keyword (like class, interface, type, etc.)
- Should use PascalCase convention (first letter of each word capitalized)

Examples of valid namespace names:

namespace MyApp {}
namespace Data_Models {}
namespace APIv2 {}

Examples of invalid namespace names:

namespace 123App {}      // Starts with number
namespace my-app {}      // Contains hyphen
namespace class {}       // Reserved keyword

Common syntax mistakes include:
- Missing opening brace: namespace MyNamespace (no {)
- Missing closing brace: namespace MyNamespace { (no })
- Extra semicolons: namespace MyNamespace;; {
- Missing namespace keyword entirely

Check for these patterns in your code. If you're using a code editor with TypeScript support, it should highlight these syntax errors.

If you're using nested namespaces, ensure each level has a name:

// Correct nested namespaces
namespace Outer {
  export namespace Inner {
    // Code here
  }
}

// Also valid with dot notation
namespace Outer.Inner {
  // Code here
}

// ERROR - missing inner namespace name
namespace Outer {
  export namespace {  // Missing name!
    // Code here
  }
}

Make sure every namespace keyword is followed by a valid identifier.

For modern TypeScript projects, consider using ES6 modules instead of namespaces. Namespaces are a TypeScript-specific feature, while modules are the standard JavaScript way to organize code.

Convert namespace to module:

// Old namespace approach
namespace Utilities {
  export function formatDate(date: Date): string {
    return date.toISOString();
  }
}

// Modern module approach
// utilities.ts
export function formatDate(date: Date): string {
  return date.toISOString();
}

// consumer.ts
import { formatDate } from './utilities';

Modules provide better tooling support, tree-shaking, and align with modern JavaScript practices.

Run the TypeScript compiler with detailed error output to pinpoint the exact location:

npx tsc --noEmit
# or for specific file
npx tsc your-file.ts --noEmit

The compiler will show the file name and line number where the error occurs. You can also use the --pretty flag for more readable output.

If using an IDE like VS Code, check the "Problems" panel (Ctrl+Shift+M) for detailed error information with clickable links to the problematic code.