The tiny all-in-one development tool for modern web apps, in a single 2mb file with no dependencies.
All the features you'd expect and more, from development to production:
🔨 No entry points or pages to configure - just HTML files with <script type=module>
🦦 Safely import "packages"
from npm without installation
📦 Smart bundling and caching for npm dependencies
↻ Hot reloading for modules, Preact components and CSS
⚡️ Lightning-fast JSX support that you can debug in the browser
💄 Import CSS files and CSS Modules (*.module.css
)
🔩 Out-of-the-box support for TypeScript
📂 Static file serving with hot reloading of CSS and images
🗜 Highly optimized Rollup-based production output (wmr build
)
📑 Crawls and pre-renders your app's pages to static HTML at build time
🏎 Built-in HTTP2 in dev and prod (wmr serve --http2
)
🔧 Supports Rollup plugins, even in development where Rollup isn't used
Create a new project in seconds using create-wmr:
npm init wmr your-project-name
or
yarn create wmr your-project-name
💁 If you'd like ESLint to be set up for you, add
--eslint
to the command. Note: this will use 150mb of disk space.
While it's best to use the quickstart method above, WMR caters to folks who want to start from scratch too.
There isn't really anything WMR-specific to set up - the steps here are essentially the what you would do to use a simple HTTP server.
1. First, install wmr
using npm or yarn:
npm i -D wmr
# or:
yarn add -D wmr
🔥 You can also use
npx wmr
anywhere!
2. Next you'll want to create a public/index.html
file. You can use this example, though there's really nothing special about this HTML file. Just make sure your scripts are ES Modules by including type="module"
:
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="/style.css" />
</head>
<body>
<script type="module" src="/index.js"></script>
</body>
</html>
💁 Why
public/
? Keeping your code and assets inpublic/
prevents files likenode_modules
andpackage.json
from being accessed by browsers. It also helps separate your web-facing code from other things like build scripts and output files. WMR auto-detects yourpublic/
directory, or you can specify your own by passing--public src
to any of the commands.
3. To test things out, create that index.js
file and add a simple Preact component to it:
import { render } from 'preact';
function App() {
return <h1>Hello World!</h1>;
}
render(<App />, document.body);
4. Now we can add some scripts to our package.json
. There's one for starting the dev server, another to create a production build. A third script serves that production build for easy local testing:
{
"scripts": {
"start": "wmr",
"build": "wmr build",
"serve": "wmr serve --http2"
}
}
preact/compat
is our compatibility layer that allows you to leverage the many libraries of the React ecosystem and use them with Preact. If this is something you'd like to use with WMR you can add an alias
section as well to your package.json
:
{
"alias": {
"react": "preact/compat",
"react-dom": "preact/compat"
}
}
5. You're all set! As an extra step, if you'd like WMR to prerender your application to static HTML during production builds, replace render()
with preact-iso:
-import { render } from 'preact';
+import hydrate from 'preact-iso/hydrate';
function App() {
return <h1>Hello World!</h1>;
}
-render(<App />, document.body);
+hydrate(<App />);
+export async function prerender(data) {
+ // we use dynamic import to prevent this from being loaded in the browser:
+ return (await import('preact-iso/prerender')).default(<App {...data} />);
+}
WMR supports a wmr.config.js
(or wmr.config.mjs
) configuration file, which can be used to set WMR's options and inject Rollup plugins or Polka/Express middleware.
You can export a default
config function applied to all WMR commands, or individual functions for start
, build
and serve
:
// wmr.config.mjs
import someRollupPlugin from '@rollup/plugin-xyz';
/** @param {import('wmr').Options} config */
export default async function (config) {
if (config.mode === 'build') {
config.plugins.push(
// add any Rollup plugins:
someRollupPlugin()
);
}
if (config.mode === 'serve') {
config.middleware.push(
// add any Polka middleware:
function myPolkaMiddleware(req, res, next) {
res.setHeader('X-Foo', 'bar');
next();
}
);
}
}
// Or configure each WMR command separately:
export async function start(config) {
// equivalent to `config.mode === 'start'`
}
export async function build(config) {
// equivalent to `config.mode === 'build'`
}
export async function serve(config) {
// equivalent to `config.mode === 'serve'`
}
Note: remember to add
"type":"module"
to your package.json or use the.mjs
file extension to make the file a JS module.
Most applications can be built with WMR without any configuration or plugins. However, sometimes a bit of configuration can help optimize the output or simplify your development workflow.
WMR supports Rollup plugins, and there's a growing list of configurations and recipes in the wiki, including: