I have have build process that is managed by Webpack. It bundles all my files up and generates a single bundle.js file. Very typical pattern.

However, when I include that file bundle.js in a webpage, the exported default function is undefined. Why can't I access that exported function from the global scope on a webpage?

Here is my webpack config:

const path = require('path');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
    entry: './src/js/index.js',
    output: {
        path: path.resolve('dist'),
        filename: 'bundle.js',
    },
    performance: {
        hints: false,
    },
    resolve: {
        modules: ['node_modules', path.join(__dirname, 'src'), 'assets'],
    },
    module: {
        rules: [
            {
                test: /\.(sa|sc|c)ss$/,
                use: [MiniCssExtractPlugin.loader, 'css-loader', 'sass-loader'],
            },
            {
                test: /\.js$/,
                exclude: /node_modules/,
                use: 'babel-loader',
            },
            {
                test: /\.(eot|svg|ttf|woff|woff2)$/,
                use: 'file-loader',
            },
        ],
    },
    plugins: [
        new MiniCssExtractPlugin({
            filename: `bundle.css`,
        }),
    ],
};

Here is a simplified src/js/index.js:

import util from './util';
import as dependency from 'external-library';
import EventEmitter from 'events';

/**
 * MyLibrary module
 * @module MyLibrary
 * @class
 * @param {MyLibraryOptions} options - Options to initialize the module with
 * @returns {Object} MyLibrary instance
 */
export default function MyLibrary(options) {
    if (!(this instanceof MyLibrary)) {
        return new MyLibrary(options);
    }
    
    //...Do a bunch of stuff.

}

The goal is to include bundle.js on a webpage and access in a script tag such as:

var instance = new MyLibrary({option_1: value, ...})

However, when I do this MyLibrary is always undefined.

UPDATE:

After adding the library property as in the webpack config, MyLibrary is not undefined, but I can't call it. It's a module now.

UPDATE 2 --> SOLUTION:

module.exports = {
    entry: './src/js/index.js',
    output: {
        library: 'MyLibrary',
        libraryTarget: 'umd',
        libraryExport: 'default',
        path: path.resolve('dist'),
        filename: 'bundle.js',
   }
...

I have have build process that is managed by Webpack. It bundles all my files up and generates a single bundle.js file. Very typical pattern.

However, when I include that file bundle.js in a webpage, the exported default function is undefined. Why can't I access that exported function from the global scope on a webpage?

Here is my webpack config:

const path = require('path');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
    entry: './src/js/index.js',
    output: {
        path: path.resolve('dist'),
        filename: 'bundle.js',
    },
    performance: {
        hints: false,
    },
    resolve: {
        modules: ['node_modules', path.join(__dirname, 'src'), 'assets'],
    },
    module: {
        rules: [
            {
                test: /\.(sa|sc|c)ss$/,
                use: [MiniCssExtractPlugin.loader, 'css-loader', 'sass-loader'],
            },
            {
                test: /\.js$/,
                exclude: /node_modules/,
                use: 'babel-loader',
            },
            {
                test: /\.(eot|svg|ttf|woff|woff2)$/,
                use: 'file-loader',
            },
        ],
    },
    plugins: [
        new MiniCssExtractPlugin({
            filename: `bundle.css`,
        }),
    ],
};

Here is a simplified src/js/index.js:

import util from './util';
import as dependency from 'external-library';
import EventEmitter from 'events';

/**
 * MyLibrary module
 * @module MyLibrary
 * @class
 * @param {MyLibraryOptions} options - Options to initialize the module with
 * @returns {Object} MyLibrary instance
 */
export default function MyLibrary(options) {
    if (!(this instanceof MyLibrary)) {
        return new MyLibrary(options);
    }
    
    //...Do a bunch of stuff.

}

The goal is to include bundle.js on a webpage and access in a script tag such as:

var instance = new MyLibrary({option_1: value, ...})

However, when I do this MyLibrary is always undefined.

UPDATE:

After adding the library property as in the webpack config, MyLibrary is not undefined, but I can't call it. It's a module now.

UPDATE 2 --> SOLUTION:

module.exports = {
    entry: './src/js/index.js',
    output: {
        library: 'MyLibrary',
        libraryTarget: 'umd',
        libraryExport: 'default',
        path: path.resolve('dist'),
        filename: 'bundle.js',
   }
...

• javascript
• webpack

• Is the last bit of code running the browser? – Calder White Commented Jul 13, 2019 at 21:17
• @CalderWhite Yes, I get an error that MyLibrary is undefined. – calbear47 Commented Jul 13, 2019 at 21:18
• How did you include the js in the webpage? <script src=".."> or some other way? – h00ligan Commented Feb 8, 2022 at 18:01
• @h00ligan That's correct. I just included my JS file with a script(in my case, bundle.js) tag before my library instantiates. – calbear47 Commented Feb 8, 2022 at 18:15

1 Answer 1

In webpack the default scope is not global. It contains all your code in an anonymous function. To expose your library to the global scope of the browser, use this answer.

Your webpack config would look like this:

const path = require('path');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
    entry: './src/js/index.js',
    output: {
        library: 'MyLibrary',
        path: path.resolve('dist'),
        filename: 'bundle.js',
    },
    performance: {
        hints: false,
    },
    resolve: {
        modules: ['node_modules', path.join(__dirname, 'src'), 'assets'],
    },
    module: {
        rules: [
            {
                test: /\.(sa|sc|c)ss$/,
                use: [MiniCssExtractPlugin.loader, 'css-loader', 'sass-loader'],
            },
            {
                test: /\.js$/,
                exclude: /node_modules/,
                use: 'babel-loader',
            },
            {
                test: /\.(eot|svg|ttf|woff|woff2)$/,
                use: 'file-loader',
            },
        ],
    },
    plugins: [
        new MiniCssExtractPlugin({
            filename: `bundle.css`,
        }),
    ],
};