Run Webpack compiler as Express.js/Browsersync middleware

Usage no npm install needed!

<script type="module">
  import webpackMiddleware from 'https://cdn.skypack.dev/webpack-middleware';



Run Webpack compiler as Express.js/Browsersync middleware

Note: This is a fork from webpack-dev-middleware with the only difference that it supports configurations with mixed web/node.js bundles (great for isomorphic apps).

What is it?

It's a simple wrapper middleware for webpack. It serves the files emitted from webpack over a connect server.

It has a few advantages over bundling it as files:

  • No files are written to disk, it handle the files in memory
  • If files changed in watch mode, the middleware no longer serves the old bundle, but delays requests until the compiling has finished. You don't have to wait before refreshing the page after a file modification.
  • I may add some specific optimization in future releases.

Getting Started

import webpack from 'webpack';
import webpackMiddleware from 'webpack-middleware';
import webpackConfig from './webpack.config.js'; // <- array of Webpack configs
import runNode from './runNode.js';

// Launch Webpack compiler in watch mode
const wp = webpackMiddleware(webpack(webpackConfig));

// Launch Node.js app in a child process
runNode('./build/server.js').then(() => {
  // Launch Browsersync dev server in proxy mode
  const bs = require('browser-sync').create();
    proxy: {
      target: 'localhost:3000', // <- where Node.js app is running
      middleware: [wp]
}, (err) => console.error(err));

Configuration Options

    // webpack options
    // webpackMiddleware takes a Compiler object as first parameter
    // which is returned by webpack(...) without callback.
    entry: '...',
    output: {
        path: '/'
        // no real path is required, just pass '/'
        // but it will work with other paths too.
}), {
    // all options optional

    noInfo: false,
    // display no info to console (only warnings and errors)

    quiet: false,
    // display nothing to the console

    lazy: true,
    // switch into lazy mode
    // that means no watching, but recompilation on every request

    watchOptions: {
        aggregateTimeout: 300,
        poll: true
    // watch options (only lazy: false)

    publicPath: '/assets/',
    // public path to bind the middleware to
    // use the same as in webpack

    headers: { 'X-Custom-Header': 'yes' },
    // custom headers

    stats: {
        colors: true
    // options for formatting the statistics

Advanced API

This part shows how you might interact with the middleware during runtime:

  • close(callback) - stop watching for file changes

    var webpackDevMiddlewareInstance = webpackMiddleware(/* see example usage */);
    // After 10 seconds stop watching for file changes:
    }, 10000);
  • invalidate() - recompile the bundle - e.g. after you changed the configuration

    var compiler = webpack(/* see example usage */);
    var webpackDevMiddlewareInstance = webpackMiddleware(compiler);
      // After a short delay the configuration is changed
      // in this example we will just add a banner plugin:
      compiler.apply(new webpack.BannerPlugin('A new banner'));
      // Recompile the bundle with the banner plugin:
    }, 1000);
  • waitUntilValid(callback) - executes the callback if the bundle is valid or after it is valid again:

    var webpackDevMiddlewareInstance = webpackMiddleware(/* see example usage */);
      console.log('Package is in a valid state');

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