Module.exports and es6 Import

Question

React with babel. I have this confusion with imports and module.exports. I assume babel when converting the ES6 code to ES5 converts the imports and exports to require and module.exports respectively.

If i export a function from one module and import the function in another module, the code executes fine. But if i export the function with module.exports and import using "import" the error is thrown at runtime saying it is not a function.

I cooked up an example.

// Tiger.js
function Tiger() {
    function roar(terrian){
        console.log('Hey i am in ' +  terrian + ' and i am roaing');
    };
    return roar;
}

module.exports = Tiger;

// animal.js
import { Tiger } from './animals';

var animal = Tiger();
animal("jungle");

I used babel with preset es2015 to transcompile it. This gives me the following error

Uncaught TypeError: (0 , _animals.Tiger) is not a function

But if i remove the module.exports = Tiger; And replace it with export { Tiger }; It works fine.

What am i missing here??

EDIT: I am using browserify as the module bundler.

Answer 1

export { Tiger } would be equivalent to module.exports.Tiger = Tiger .

Conversely, module.exports = Tiger would be equivalent to export default Tiger .

So when you use module.exports = Tiger and then attempt import { Tiger } from './animals' you're effectively asking for Tiger.Tiger .

Answer 2

If you would like to import:

module.exports = Tiger

you may use following construction:

import * as Tiger from './animals'

Then it will work.

Another option is changing the export as described by @Matt Molnar but it is only possible if you are the author of the imported code.

Answer 3

When module.exports is not set it points to an empty object ( {} ). When you do module.exports = Tiger , you are telling the runtime the object being exported from that module is the Tiger object (instead of the default {} ), which in this case is a function.
Since you want to import that same function, the way to import is using the default import ( import tiger from './tiger' ). Otherwise, if you want to use named import ( import { tiger } from './tiger' ) you must change the module.exports object or use export keyword instead of module.exports object.

Default import/export:

// tiger.js
module.exports = tiger;
// or
export default function tiger() { ... }

// animal.js
import tiger from './tiger';

Named import/export:

// tiger.js
module.exports = { tiger };
// or
module.exports.tiger = tiger
// or
export const tiger = () => { ... }
// or
export function tiger() => { ... }

// animal.js
import { tiger } from './tiger';

Answer 4

For me I am trying to apply this to a webpack.config.ts. The above does not work import * as X from "./X"; I get another error.

Module.exports with es6 import for webpack.config.ts in typescript

const getConfig = ( appDir: string, distDir: string, env: any, args: any ): webpack.Configuration => {
    const config: webpack.Configuration = {
        return config;
    };
};

module.exports = getConfig;