Aleph.js

Plugin API

In Aleph.js, a Plugin is an object with a name and a setup method. The setup method will be invoked once before the Aleph server runtime is initialized.

type Plugin = {
  name: string;
  setup(aleph: Aleph): Promise<void> | void;
}

Writing First Aleph Plugin

Here's a simple plugin example that allows you to add a virtual dist file to the server:

// aleph.config.ts

import type { Config, Plugin } from 'https://deno.land/x/aleph/types.d.ts'

const helloPlugin: Plugin = {
  name: 'hello-plugin',
  setup: aleph => {
    aleph.addDist(
      'hello.js',
      (new TextEncoder()).encode('console.log("Hello World!")'),
    )
  },
}

export default <Config> {
  plugins: [helloPlugin],
}

then you can download the hello.js file from http://localhost:8080/_aleph/hello.js

Using Aleph Object

The Aleph object is the server runtime reference of Aleph.js, that allows you to hack into the server runtime lifecycle.

Properties

  • mode specifies the build mode that should be 'development' or 'production'.
    {
  name: 'plugin-name',
  setup: aleph => {
    if (aleph.mode === 'development') {
      console.log('development mode')
    }
  }
}
  • workingDir shows the application absolute path that is a read-only property.
    {
  name: 'plugin-name',
  setup: async aleph => {
    const fp = path.join(aleph.workingDir, 'data.json')
    const data = JSON.parse(await Deno.readFile(fp))
  }
}
  • config is an object parsed from 'aleph.config.ts', you can update it to add more options, check Config to get more usage.
    {
  name: 'plugin-name',
  setup: async aleph => {
    aleph.config.env['foo'] = await getEnv('foo')
    aleph.config.server.headers['X-Foo'] = 'bar'
  }
}

Methods

  • addDist adds a virtual dist file to the server, then access it from /_aleph/$NAME.
    {
  name: 'plugin-name',
  setup: async aleph => {
    aleph.addDist('hello.js', (new TextEncoder).encode('console.log("Hello World!")'))
  }
}
  • addModule adds a virtual module to the server, that can be a page or API.
    {
  name: 'plugin-name',
  setup: async aleph => {
    // adds a virtual module
    aleph.addModule('https://deno.land/x/aleph/hello.ts', 'export default { ... }')
    // adds a virtual module as API
    aleph.addModule('api/hello.ts', 'export const handler = (req) => { ... }')
    // adds a virtual module as Page
    aleph.addModule('pages/hello.tsx', 'export defaut function Hello() { ... }')
  }
}

    The available module type: js, jsx, ts, tsx and css.

Lifecycle Hooks

  • onResolve customizes how Aleph does path resolution.

    {
  name: 'plugin-name',
  setup: async aleph => {
    aleph.onResolve(/.(md|markdown)$/, specifier => {
      return {
        // rewrite the import specifier to other
        specifier: specifier,
        // allows modules as page when it is in the `pages/` dir
        asPage: true,
        // allows modules to be updated at runtime during development
        acceptHMR: true,
        // don't download/compile remote modules, let browser handles it
        external: false,
        // defines any data that will be passed to the next `onResolve` hook
        data: {} as any
      }
    })
  }
}

  • onLoad allows you to load any content as a JS module, for example load markdown as pages.

    {
  name: 'plugin-name',
  setup: async aleph => {
    // the `data` is passed from previous `onResolve` hook
    aleph.onLoad(/.(md|markdown)$/, async ({ specifier, data }) => {
      // loads and caches content as `Uint8Array` by the specifier
      const { content } = await aleph.loadModule(specifier)

      return {
        // specifies the output code type (Available type: `css` | `js` | `jsx` | `ts` | `tsx`)
        type: 'js',
        // defines transformed code in above type
        code: mdjs(content),
        // provides source map if available
        map: undefined,
      }
    })
  }
}

  • onTransform injects code to compiled modules, you need to return an object with modified code or undefined to keep raw code.

    {
  name: 'plugin-name',
  setup: async aleph => {
    // inject code to the `main.js`
    aleph.onTransform('main', ({ module, code, map }) => {
      return {
        code: code + '\nconsole.log(":)")',
        map: undefined, // provides source map if available
      }
    })
    // inject code to modules when the HMR is avaiable
    aleph.onTransform('hmr', ({ module, code, map }) => {
      return {
        code: code + '\nimport.meta.hot.accept(__REACT_REFRESH__)',
        map: undefined, // provides source map if available
      }
    })
    // inject code to page modules
    aleph.onTransform(/pages\//, ({ module, code, map }) => {
      return {
        code: code + `\nconsole.log("current module is ${module.specifier}")`,
        map: undefined, // provides source map if available
      }
    })
  }
}

  • onRender modifies the SSR output HTML and data.

    {
  name: 'plugin-name',
  setup: async aleph => {
    aleph.onRender(({path, html, data}) => {
      html.headElements.push(`<script src="/gtag.js?id=${GTAG}" async></script>`)
    })
  }
}

Examples

The example plugins below are meant to give you an idea of the different types of things you can do with the plugin API.

WASM loader

This example plugin is a loader allows you to import .wasm files into JS module.

import type { Plugin } from 'https://deno.land/x/aleph/types.d.ts'

export default <Plugin> {
  name: 'wasm-loader',
  setup: aleph => {
    aleph.onLoad(/\.wasm$/i, async ({ specifier }) => {
      const { content } = await aleph.fetchModule(specifier)
      return {
        code: [
          `const wasmBytes = new Uint8Array([${content.join(',')}])`,
          'const wasmModule = new WebAssembly.Module(wasmBytes)',
          'const { exports } = new WebAssembly.Instance(wasmModule)',
          'export default exports',
        ].join('\n'),
      }
    })
  },
}

Now you can import .wasm files as ES Module:

import wasm from '../lib/42.wasm'

const answer = wasm.main() // 42

Tailwind JIT for JSX

Aleph's compiler will record the static class names in JSX files, with that you can create css on demand for tailwind vary easily.

import { basename } from 'https://deno.land/std/path/mod.ts'
import type { Plugin } from 'https://deno.land/x/aleph/types.d.ts'

export default <Plugin> {
  name: 'tailwind-loader',
  setup: aleph => {
    aleph.onTransform(/\.(j|t)sx$/i, async ({ module, code }) => {
      const { specifier, deps, sourceHash, jsxStaticClassNames } = module
      if (jsxStaticClassNames?.length) {
        const url = specifier.replace(/\.(j|t)sx$/i, '') + '.tailwind.css'
        const css = tailwindCompile(jsxStaticClassNames)
        const { jsFile } = aleph.addMoudle(url, css)

        // support SSR
        deps.push({specifier: url})

        return {
          // import tailwind css
          code: `import "./${basename(jsFile)}#${sourceHash.slice(0,8)}";` + code
        }
      }
    })
  }
}

Google Analytics

This example plugin shows how to insert custom scripts to SSR output HTML.

import { basename } from 'https://deno.land/std/path/mod.ts'
import type { Plugin } from 'https://deno.land/x/aleph/types.d.ts'

export default <Plugin> {
  name: 'google-analytics-plugin',
  setup: aleph => {
    const id = Deno.env.get('GTAG')
    if (id && aleph.mode === 'production') {
      aleph.onRender(({ html }) => {
        html.scripts.push(
          {
            src: `https://www.googletagmanager.com/gtag/js?id=${encodeURIComponent(id)}`,
            async: true
          },
          `window.dataLayer = window.dataLayer || [];
          function gtag() {
            dataLayer.push(arguments);
          }
          gtag('js', new Date());
          gtag('config', ${JSON.stringify(id)});`
        )
      })
    }
  }
}

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