Preact server rendered, partial hydration and islands for everyone!

• Highlights
• Installation
• Usage
• Concepts
  • File Name Extensiom
  • Top Level comments
  • Lazy Hydration
• Limitations
• Example Configs
• How
• FAQs
• Contributing

• Tiny
• Tree Shakeable
• Flexibile / Not dependent on folder structure
  • Use either .island.js file extensions for initialize islands
  • or //@island top level file comments
  • Automatic detection of an island (since v0.1.2)
• Lazy Hydration Modifiers - //@island lazy

The installation differs based on which plugin you wish to use.

npm i esbuild @barelyhuman/preact-island-plugins preact

npm i rollup preact @barelyhuman/preact-island-plugins @rollup/plugin-babel @rollup/plugin-node-resolve

if using typescript, you should also add that when using rollup

npm i @rollup/plugin-typescript

// Single Import
const preactIslands = require('@barelyhuman/preact-island-plugins')

preactIslands.rollup(options)
// or
preactIslands.esbuild(options)

// Tree Shakeable Import

// For rollup
const preactIslands = require('@barelyhuman/preact-island-plugins/rollup')

// for esbuild
const preactIslands = require('@barelyhuman/preact-island-plugins/esbuild')

Both bundlers use the same Options type, please read through the API options below to configure the behaviour of the island generation

export interface Options {
  // The working directory of the project, Defaults to '.'
  rootDir: string
  // If using `atomic` components, use the baseURL to specific the path where the JS Assets will be available
  baseURL: string
  // when true, each island has it's own script for lazy loading JS and Interactivity
  atomic?: boolean
  // If working with bundlers where hashing isn't available, you can set the `hash` to true to get browsers
  //  to load the correct JS after loads
  hash?: boolean
  // The plugins use your bundler (rollup, esbuild, etc) to also bundle the client asset with it's own imports
  // so the `client` options define the behavior for that
  client: {
    // path of where to output the bundled components
    output: string
  }
}

The overall idea is to be able to define islands without thinking about it.

The plugins provide 2 ways to do this.

You name the file .island.js or .island.tsx and this will generate the island files for you according to your build configs. Make sure you go through the playground to better understand this.

The other options is to prefix the code with //@island and this is to be done where you start the file without knowing if it's going to be an islad or not.

This might look, something like this

//@island

export default function Counter() {
  const [count, setCount] = useState(0)
  return <>{count}</>
}

The islands generated by this plugin is already lazy loaded, so you don't have to ever set it up and the browser will take care of handling the cache of the file. Though, we do provide with lazy hydration which can help with performance where the JS is downloaded earlier but is not applied to the DOM element unless it's in view.

It would look something like this

//@island lazy

export default function Counter() {
  const [count, setCount] = useState(0)
  return <>{count}</>
}

You can also define the threshold of visibility by adding a number from 0 to 1 to the lazy modifier.

• 0 - Hydrate as soon as the element is in view.
• 0.5(default) - Hydrate after at least 50% of the element is in view
• 1 - Hydrate after the whole element is in view

//@island lazy:0.2
//              ^ hydrate Counter after 20% of the element is in the viewport

export default function Counter() {
  const [count, setCount] = useState(0)
  return <>{count}</>
}

• Only allows Single default export to be an island right now
• Bug with Text based containers #4

// build.js
// for esbuild
const esbuild = require('esbuild')
const preactIslands = require('@barelyhuman/preact-island-plugins/esbuild')

esbuild
  .build({
    entryPoints: ['./server.js'],
    format: 'cjs',
    target: 'node16',
    platform: 'node',
    bundle: true,
    jsx: 'automatic',
    jsxImportSource: 'preact',
    loader: {
      '.js': 'jsx',
    },
    outdir: 'dist',
    plugins: [preactIslands()],
  })
  .then(_ => process.exit(0))
  .catch(_ => process.exit(1))

For rollup, it might look something like this

// rollup.config.js
const { nodeResolve } = require('@rollup/plugin-node-resolve')
const { babel } = require('@rollup/plugin-babel')
const preactIslands = require('@barelyhuman/preact-island-plugins/rollup')
const { DEFAULT_EXTENSIONS } = require('@babel/core')
const typescript = require('@rollup/plugin-typescript').default

/**
 * @type {import("rollup").RollupOptions}
 */
module.exports = {
  input: 'server.js',
  output: {
    dir: 'dist',
    format: 'cjs',
  },
  plugins: [
    // helper plugins to handle typescript for the remaining of the server
    typescript({
      compilerOptions: {
        jsx: 'react-jsx',
        jsxImportSource: 'preact',
      },
    }),
    preactPlugin(),
    // subset handlers for the remaining of the server to handle jsx
    babel({
      plugins: [
        [
          '@babel/plugin-transform-react-jsx',
          { runtime: 'automatic', importSource: 'preact' },
        ],
      ],
      babelHelpers: 'bundled',
      extensions: [...DEFAULT_EXTENSIONS, '.ts', '.tsx'],
    }),
  ],
}

The source code is pretty small but if it's just the concept behind that you wish to understand, then please keep reading this.

Islands are normally interactive elements or tiny apps that are mounted on parts of a static html. This is done to minimize the amount of JS sent to the client by your app. A lot of frameworks already handle this for you, a few examples are:

• Astro.build
• Deno Fresh

There's tiny differences in the implementations that each of us use but the overall concept remains same. The only reason to choose this plugin would be that you don't have to migrate your whole app to the framework just to enjoy islands or get rid of let's say something like old JQuery dependencies. I like JQuery but it'll probably be easier to use something better at handling state today.

This can also be used by someone who doesn't like frameworks and would prefer working with their own set of choices / decisions in their tech stack.

Overall, it's tiny enough to build your own framework on top off and also shove it down the structure you already have.

What on earth in islands?

• Glad you asked, You can read about it on here

Who's this library/plugins for?

• Anyone who wishes to setup partial hydration on an existing server codebase.
• People building meta frameworks for preact

Examples, please?

• Sure, you can go through the playground folder to see how to use it with esbuild and rollup with an express server. If you have any problems setting it up still, feel free to raise an issue.

Contributions are welcome! Here's how you can get involved:

1. Fork the project repository.
2. Create a new branch for your feature or bug fix.
3. Make your changes and commit them, following the project's code style guidelines.
4. Push your changes to your forked repository.
5. Submit a pull request with a description of your changes.

This project is licensed under the MIT License.