How to use namespaces with import in TypeScript

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A solution with namespaces (not recommended)

To resolve your issue, you can export your namespace:

// UtilBase.ts
import * as path from "path";
export namespace My.utils {
    export class UtilBase {
        protected fixPath(value: string): string {
            return value.replace("https://stackoverflow.com/", path.sep);
        }
   }
}

Then, you should be able to import it:

// UtilOne.ts
import {My} from './UtilBase';
namespace My.utils {
    export class UtilOne extends My.utils.UtilBase {
    }
}

However, if the purpose is to organize the code, it is a bad practice to use namespaces and (ES6) modules at the same time. With Node.js, your files are modules, then you should avoid namespaces.

Use ES6 modules without namespaces

TypeScript supports the syntax of ES6 modules very well:

// UtilBase.ts
import * as path from "path";
export default class UtilBase {
    protected fixPath(value: string): string {
        return value.replace("https://stackoverflow.com/", path.sep);
    }
}

// UtilOne.ts
import UtilBase from './UtilBase';
export default class UtilOne extends UtilBase {
}

It is the recommended way. ES6 modules prevent naming conflicts with the ability to rename each imported resource.

It will work on Node.js.

For a good introduction to the ES6 modules syntax, read this article.

Use a file tsconfig.json instead of /// <reference

Notice: The syntax /// <reference is replaced by the file tsconfig.json. An example for Node.js:

// tsconfig.json
{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es6"
  },
  "exclude": [
    "node_modules"
  ]
}

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