Q:

Node module doesn't work after webpack build

I'm having some problems with building own node module for my react  apps. I need this to prepare some common functions for couple of my react apps and I want them to be placed in separated node module. So, I created the module and it looks like that:

-src
--index.js
-package.json

index.js file:
export const myFunction = () => {
  return 'Some nice text';
}

package.json
{
  "name": "mymodule",
  "version": "1.0.0",
  "description": "",
  "main": "src/index.js",
  "scripts": {
    "test": "npm test"
  },
  "author": "",
  "license": "ISC",
}

In the react app (consumer project) I'm importing the function:
import { myFunction } from 'mymodule';

console.log(myFunction());

Till now, everything works fine. In the console I see the text Some nice text.
Now, I'm trying to build my module with webpack 4 so I updated my package.json file:
{
  "name": "mymodule",
  "version": "1.0.0",
  "description": "",
  "main": "dist/main.js", <-- this is the file build by webpack
  "scripts": {
    "build": "webpack"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "webpack": "^4.21.0",
    "webpack-cli": "^3.1.2"
  }
}

and rebuild both projects. Then I see in the console following error:
Uncaught TypeError: (0 , _mymodule.myFunction) is not a function
    at eval (index.jsx:47)
    at Object../src/index.jsx (main.js:8559)
    at __webpack_require__ (main.js:20)
    at eval (webpack:///multi_(:8080/webpack)-dev-server/client?:3:18)
    at Object.0 (main.js:9057)
    at __webpack_require__ (main.js:20)
    at main.js:84
    at main.js:87

EDIT:
I added babel as suggested and turned off minimization. This is how my dist/main.js file looks like:
/******/ (function(modules) { // webpackBootstrap
/******/    // The module cache
/******/    var installedModules = {};
/******/
/******/    // The require function
/******/    function __webpack_require__(moduleId) {
/******/
/******/        // Check if module is in cache
/******/        if(installedModules[moduleId]) {
/******/            return installedModules[moduleId].exports;
/******/        }
/******/        // Create a new module (and put it into the cache)
/******/        var module = installedModules[moduleId] = {
/******/            i: moduleId,
/******/            l: false,
/******/            exports: {}
/******/        };
/******/
/******/        // Execute the module function
/******/        modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);
/******/
/******/        // Flag the module as loaded
/******/        module.l = true;
/******/
/******/        // Return the exports of the module
/******/        return module.exports;
/******/    }
/******/
/******/
/******/    // expose the modules object (__webpack_modules__)
/******/    __webpack_require__.m = modules;
/******/
/******/    // expose the module cache
/******/    __webpack_require__.c = installedModules;
/******/
/******/    // define getter function for harmony exports
/******/    __webpack_require__.d = function(exports, name, getter) {
/******/        if(!__webpack_require__.o(exports, name)) {
/******/            Object.defineProperty(exports, name, { enumerable: true, get: getter });
/******/        }
/******/    };
/******/
/******/    // define __esModule on exports
/******/    __webpack_require__.r = function(exports) {
/******/        if(typeof Symbol !== 'undefined' && Symbol.toStringTag) {
/******/            Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' });
/******/        }
/******/        Object.defineProperty(exports, '__esModule', { value: true });
/******/    };
/******/
/******/    // create a fake namespace object
/******/    // mode & 1: value is a module id, require it
/******/    // mode & 2: merge all properties of value into the ns
/******/    // mode & 4: return value when already ns object
/******/    // mode & 8|1: behave like require
/******/    __webpack_require__.t = function(value, mode) {
/******/        if(mode & 1) value = __webpack_require__(value);
/******/        if(mode & 8) return value;
/******/        if((mode & 4) && typeof value === 'object' && value && value.__esModule) return value;
/******/        var ns = Object.create(null);
/******/        __webpack_require__.r(ns);
/******/        Object.defineProperty(ns, 'default', { enumerable: true, value: value });
/******/        if(mode & 2 && typeof value != 'string') for(var key in value) __webpack_require__.d(ns, key, function(key) { return value[key]; }.bind(null, key));
/******/        return ns;
/******/    };
/******/
/******/    // getDefaultExport function for compatibility with non-harmony modules
/******/    __webpack_require__.n = function(module) {
/******/        var getter = module && module.__esModule ?
/******/            function getDefault() { return module['default']; } :
/******/            function getModuleExports() { return module; };
/******/        __webpack_require__.d(getter, 'a', getter);
/******/        return getter;
/******/    };
/******/
/******/    // Object.prototype.hasOwnProperty.call
/******/    __webpack_require__.o = function(object, property) { return Object.prototype.hasOwnProperty.call(object, property); };
/******/
/******/    // __webpack_public_path__
/******/    __webpack_require__.p = "";
/******/
/******/
/******/    // Load entry module and return exports
/******/    return __webpack_require__(__webpack_require__.s = 0);
/******/ })
/************************************************************************/
/******/ ([
/* 0 */
/***/ (function(module, __webpack_exports__, __webpack_require__) {

"use strict";
__webpack_require__.r(__webpack_exports__);
/* harmony export (binding) */ __webpack_require__.d(__webpack_exports__, "myFunction", function() { return myFunction; });
function myFunction() {
  return 'aaaaaabbbb';
}

Has somebody faced similar issue? Thanks in advance!

A:

The problem is with build config. This build file doesn't export the function outside. To do it, let's add output key to webpack config:
module.exports = {
    ...
    output: {
        library: 'modulename',
        libraryTarget: 'umd',
        filename: 'main.js',
    },
    ...
};

Then, the module functions will be exported outside. 

