How to fix Namespace cannot be declared in non-module context in TypeScript

// Add this to make the file a module
export {};

// Now you can declare namespaces
namespace MyNamespace {
  export function doSomething() {
    console.log("Hello from namespace");
  }
}

// Import something to make it a module
import { something } from "./other-module";

// Or export something
export const myConstant = 42;

namespace MyNamespace {
  export function doSomething() {
    console.log("Working with", something);
  }
}

{
  "compilerOptions": {
    "module": "commonjs",  // or "es2015", "esnext", etc.
    "target": "es2015",
    // Other options...
  }
}

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

// Use:
export function formatDate(date: Date): string {
  return date.toISOString();
}

// Or group in an object:
export const Utilities = {
  formatDate(date: Date): string {
    return date.toISOString();
  }
};

// In a .d.ts file or file without imports/exports
declare global {
  interface Window {
    myCustomProperty: string;
  }
}

// This works in non-module contexts
// while namespaces would fail