How to use ES6 import/export with Webpack 4?

Question

I'm trying to get a basic ES6 import/export working with Webpack 4, and Webpack can't seem to resolve my module, though per the error message it's looking right at it:

$ make
./node_modules/.bin/webpack --mode production src/app.js -o dist/bundle.js
Hash: 6decf05b399fcbd42b01
Version: webpack 4.1.1
Time: 339ms
Built at: 2018-3-11 14:50:58
 1 asset
 Entrypoint main = bundle.js
    [0] ./src/app.js 41 bytes {0} [built]

ERROR in ./src/app.js
Module not found: Error: Can't resolve 'hello.js' in '/home/(myhomedir)/code/js/src'
 @ ./src/app.js 1:0-31 2:0-5                                    

Here's my setup (node_modules, dist etc. omitted):

$ npm ls --depth=0
.
├── [email protected]
└── [email protected]

$ tree
.
├── Makefile
└── src
    ├── app.js
    └── hello.js

Makefile:

webpack = ./node_modules/.bin/webpack --mode production
entry = src/app.js

webpack: $(entry)
    $(webpack) $(entry) -o dist/bundle.js

src/app.js:

import {hello} from "hello.js";
hello();

src/hello.js:

function hello() {
    alert("yes it's hello");
}
export { hello };

I've tried many variations on the import path in app.js, but they all get the same result: Can't resolve the module file. What am I missing?

Answer 1

You need to transpile it using babel & use babel-loader.

Also, you don't need to use make just use npm scripts.

There are mistakes like importing import { hello } from 'hello.js' instead it should be import { hello } from './hello.js' or without .js like import { hello } from './hello'

Try the following -

npm install --save-dev babel-core babel-loader babel-preset-env webpack@next webpack-cli

src/app.js

import { hello } from "./hello";
hello();

src/hello.js

function hello() {
  console.log("yes it's hello");
}
export { hello };

webpack.config.js

const path = require("path");

module.exports = {
  entry: "./src/app.js",

  output: {
    path: path.resolve(__dirname, "dist"),
    filename: "bundle.js"
  },

  module: {
    rules: [
      {
        test: /\.js$/,
        loader: "babel-loader",
        exclude: /(node_modules)/
      }
    ]
  }
};

package.json

{
  "name": "webpack-test",
  "version": "1.0.0",
  "description": "",
  "main": "webpack.config.js",
  "scripts": {
    "build": "webpack --mode development",
    "prod": "webpack --mode production",
    "start": "node dist/bundle.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "babel-core": "^6.26.0",
    "babel-loader": "^7.1.4",
    "babel-preset-env": "^1.6.1",
    "webpack": "^4.0.0-beta.3",
    "webpack-cli": "^2.0.11"
  }
}

.babelrc

{
  "presets": ["env"]
}

First run npm run build or npm run prod & then run npm run start which will log the output