heiss

Static server, which implements hot module replacement for native ES2015 modules.

Warning: This is an early prototype. It serves more as a playground for various ideas then as a finished stable tool.

Limitations

Due to the nature of implementation, it is not possible to hot reload modules in the following cases:

• export names or their count have changed.
• module, that exports mutable variable bindings (let or const).

Requirements

Server part requires node.js 8 or greater.

For the client to work properly, you'll need the browser which natively supports:

• ES2015 modules
• Dynamic import
• import.meta

Command-line

heiss <rootDirectory>

Starts a static server, serving the files from <rootDirectory>. Hot reloading will be available for every .js or .mjs file (see limitations sections above).

You can change hostname or port of the server with --host and --port arguments respectively.

HMR API

API is served as /@hmr/api module. The main function you'll need is hot. It accepts current module url as a parameter and returns object with the following methods:

• accept(dependencies: string[], updateCallback) — called when any of the specified dependencies change. dependencies can be either absolute or relative URLs. Inside the updateCallback all imports will be already updated to their new values, there is no need to re-import anything:

  import { init } from './init.mjs';
  import { hot } from '/@hmr/api';
   
  init();
   
  hot(import.meta.url).accept(['./init.mjs'], () => {
    init();
  });

• selfAccept() — marks current-module as self-accepting. In this case, current module will be automatically re-evaluted when it or any of its dependecies change:

  import { init } from './init.mjs';
  import { hot } from '/@hmr/api';
   
  init();
   
  hot(import.meta.url).selfAccept();

• dispose(callback) — called when current module is about to unload. Can be used for cleaning up any side-effects:

  import { addWidgetToDocument, removeWidgetFromDocument } from './widget.mjs';
  import { hot } from '/@hmr/api';
   
  addWidgetToDocument();
   
  hot(import.meta.url).dispose(() => removeWidgetFromDocument());

Example in the repo

npm install
npm start

After that, open http://localhost:8080 in any supported browser support and edit 'example/text.mjs'