webpack-hot-client

A client for enabling, and interacting with, webpack Hot Module Replacement.

This is intended to work in concert with webpack-dev-middleware and allows for adding Hot Module Replacement to an existing server, without a dependency upon webpack-dev-server. This comes in handy for testing in projects that already use server frameworks such as Express or Koa.

webpack-hot-client accomplishes this by creating a WebSocket server, providing the necessary client (browser) scripts that communicate via WebSockets, and automagically adding the necessary webpack plugins and config entries. All of that allows for a seamless integration of Hot Module Support.

Curious about the differences between this module and webpack-hot-middleware? Read more here.

Getting Started

To begin, you'll need to install webpack-hot-client:

$ npm install webpack-hot-client --save-dev

Gotchas

In order to use webpack-hot-client, your webpack config should include an entry option that is set to an Array of String, or an Object who's keys are set to an Array of String. You may also use a Function, but that function should return a value in one of the two valid formats.

This is primarily due to restrictions in webpack itself and the way that it processes options and entries. For users of webpack v4+ that go the zero-config route, you must specify an entry option.

It's also worth noting that webpack-hot-client adds HotModuleReplacementPlugin and the necessary entries to your webpack config for you at runtime. Including the plugin in your config manually while using this module may produce unexpected or wonky results.

Express

For setting up the module for use with an Express server, try the following:

const client = require('webpack-hot-client');
const middleware = require('webpack-dev-middleware');
const webpack = require('webpack');
const config = require('./webpack.config');

const compiler = webpack(config);
const { publicPath } = config.output;
const options = { ... }; // webpack-hot-client options

// we recommend calling the client _before_ adding the dev middleware
client(compiler, options);

app.use(middleware(compiler, { publicPath }));

Koa

Since Koa@2.0.0 was released, the patterns and requirements for using webpack-dev-middleware have changed somewhat, due to use of async/await in Koa. As such, one potential solution is to use koa-webpack, which wires up the dev middleware properly for Koa, and also implements this module. If you'd like to use both modules without koa-webpack, you may examine that module's code for implementation details.

Browser Support

Because this module leverages native WebSockets, the browser support for this module is limited to only those browsers which support native WebSocket. That typically means the last two major versions of a particular browser.

Note: We won't be accepting requests for changes to this facet of the module.

API

client(compiler, [options])

Returns an Object containing:

• close() (Function) - Closes the WebSocketServer started by the module.
• wss (WebSocketServer) - A WebSocketServer instance.

options

Type: Object

autoConfigure

Type: Boolean
Default: true

If true, automatically configures the entry for the webpack compiler, and adds the HotModuleReplacementPlugin to the compiler.

host

Type: String|Object
Default: 'localhost'

Sets the host that the WebSocket server will listen on. If this doesn't match the host of the server the module is used with, the module may not function properly. If the server option is defined, this option is ignored.

If using the module in a specialized environment, you may choose to specify an object to define client and server host separately. The object value should match { client: <String>, server: <String> }. Be aware that the client host will be used in the browser by WebSockets. You should not use this option in this way unless you know what you're doing. Using a mismatched client and server host will be unsupported by the project as the behavior in the browser can be unpredictable and is specific to a particular environment.

hot

Type: Boolean
Default: true

If true, instructs the client script to attempt hot patching of modules.

https

Type: Boolean
Default: false

If true, instructs the client script to use wss:// as the WebSocket protocol. If you're using a server setup with HTTPS, you must set this to true or the sockets cannot communicate and this module won't function properly.

logLevel

Type: String
Default: 'info'

Sets the minimum level of logs that will be displayed in the console. Please see webpack-log/#levels for valid values.

logTime

Type: Boolean
Default: false

If true, instructs the internal logger to prepend log output with a timestamp.

port

Type: Number
Default: 8081

The port the WebSocket server should listen on. It's recommended that a server instance is passed to assure there aren't any port conflicts.

reload

Type: Boolean
Default: true

If true, instructs the browser to physically refresh the entire page if / when webpack indicates that a hot patch cannot be applied and a full refresh is needed.

This option also instructs the browser whether or not to refresh the entire page when hot: false is used.

Note: If both hot and reload are false, and these are permanent settings, it makes this module fairly useless.

server

Type: Object
Default: null

If a server instance (eg. Express or Koa) is provided, the WebSocket server will attempt to attach to the server instance instead of using a separate port.

stats

Type: Object
Default: { context: process.cwd() }

An object specifying the webpack stats configuration. This does not typically need to be modified.

Webpack Build Targets

By default, webpack-hot-client is meant to, and expects to function on the 'web' build target. However, you can manipulate this by setting the WHC_TARGET environment variable. eg.

$ export WHC_TARGET=electon-renderer; webpack-serve ...

Or by setting process.env.WHC_TARGET before executing the API.

Note: Changing this value is allowed but is unsupported.

Communicating with Client WebSockets

In some rare situations, you may have the need to communicate with the attached WebSockets in the browser. To accomplish this, open a new WebSocket to the server, and send a broadcast message. eg.

const stringify = require('json-stringify-safe');
const { WebSocket } = require('ws');

const socket = new WebSocket('ws://localhost:8081'); // this should match the server settings
const data = {
  type: 'broadcast',
  data: { // the message you want to broadcast
    type: '<something fun>', // the message type you want to broadcast
    data: { ... } // the message data you want to broadcast
  }
};

socket.send(stringify(data));

Note: The data property of the message should contain the enveloped message you wish to broadcast to all other client WebSockets.

Contributing

We welcome your contributions! Please have a read of CONTRIBUTING.md for more information on how to get involved.

License

MIT