import HelloWorld from './path/to/elements/hello-world.mjs'
import enhance from '@enhance/ssr'
const html = enhance({
  elements: {
    'hello-world': HelloWorld
  }
})
console.log(html`<hello-world greeting="Well hi!"></hello-world>`)

An example custom element template for use in Server Side Rendering

Attributes added to the custom element in your markup will be passed in the attrs object nested in the passed state object.

export default function HelloWorld({ html, state }) {
  const { attrs } = state
  const { greeting='Hello World' } = attrs
  return html`
    <style scope="global">
      h1 {
        color: red;
      }
    </style>

    <h1>${greeting}</h1>

    <script type=module>
      class HelloWorld extends HTMLElement {
        constructor () {
          super()
          const template = document.getElementById('hello-world-template')
          this.attachShadow({ mode: 'open' })
            .appendChild(template.content.cloneNode(true))
        }

        connectedCallback () {
          console.log('Why hello there 👋')
        }
      }

      customElements.define('hello-world', HelloWorld)
    </script>
  `
}

The template added to the server rendered HTML page

// Output
<head>
  <style scope="global">
    h1 {
      color: red;
    }
  </style>
</head>

<body>

<script type="module">
  class HelloWorld extends HTMLElement {
    constructor () {
      super()
      const template = document.getElementById('hello-world-template')
      this.attachShadow({ mode: 'open' })
        .appendChild(template.content.cloneNode(true))
    }

    connectedCallback () {
      console.log('Why hello there 👋')
    }
  }

  customElements.define('hello-world', HelloWorld)
</script>

<template id="hello-world-template">
  <h1>Hello World</h1>
</template>

</body>

If you author slotted elements they will be added to a template keyed by the custom element's id. If no id is authored one will be added during server side render. You can extend @enhance/base-element to manage progressive enhancement of your custom element and cut down on boilerplate for your Web Component.

// Output
<head>
  <style scope="global">
    h1 {
      color: red;
    }
  </style>
</head>
<body>
<hello-world>
  <h1 slot="salutation">
    Whattap!
  </h1>
</hello-world>

<script type="module">
  class HelloWorld extends BaseElement {
    constructor () {
      super()
    }

    connectedCallback () {
      console.log('Why hello there 👋')
    }
  }

  customElements.define('hello-world', HelloWorld)
</script>

<template id="hello-world-template">
  <slot name="salutation">
    <h1>Hello World</h1>
  </slot>
</template>
</body>

Supply initital state to enhance and it will be passed along in a store object nested inside the state object.

Node

import MyStoreData from './path/to/elements/my-store-data.mjs'
import enhance from '@enhance/ssr'
const html = enhance({
  elements: {
    'my-store-data': MyStoreData
  },
  initialState: { apps: [ { users: [ { name: 'tim', id: 001 }, { name: 'kim', id: 002 } ] } ] }
})
console.log(html`<my-store-data app-index="0" user-index="1"></my-store-data>`)

Template

// Template
export default function MyStoreData({ html, state }) {
  const { attrs, store } = state
  const appIndex = attrs['app-index']
  const userIndex = attrs['user-index']
  const { id='', name='' } = store?.apps?.[appIndex]?.users?.[userIndex] || {}
  return `
<div>
  <h1>${name}</h1>
  <h1>${id}</h1>
</div>
  `
}

Attribute state can be used to pass default state to the backing Web Component. Store is used to pass previously stored data, in an easy to access way, to all components in the tree.

Slots

Enhance supports the use of slots in your custom element templates.

export default function MyParagraph({ html }) {
  return html`
<p>
  <slot name="my-text">
    My default text
  </slot>
</p>
  `
}

You can override the default text by adding a slot attribute with a value that matches the slot name you want to replace.

<my-paragraph>
  <span slot="my-text">Let's have some different text!</span>
</my-paragraph>

Unnamed slots

Enhance supports unnamed slots for when you want to create a container element that will exposes it's content from the Shadow DOM.

export default function MyParagraph({ html }) {
  return html`
<p>
  <slot>This will not render.</slot>
</p>
  `
}

<my-paragraph>
  This will render <strong>all</strong> authored children.
</my-paragraph>

Transforms

Enhance supports the inclusion of script and style transform functions. You add a function to the array of scriptTransforms and/or styleTransforms and are able to transform the contents however you wish, just return the your desired output.

import enhance from '@enhance/ssr'

const html = enhance({
  elements: {
    'my-transform-script': MyTransformScript
  },
  scriptTransforms: [
    function({ attrs, raw }) {
      // raw is the raw text from inside the script tag
      // attrs are the attributes from the script tag
      return raw + ' yolo'
    }
  ],
  styleTransforms: [
    function({ attrs, raw }) {
      // raw is the raw text from inside the style tag
      // attrs are the attributes from the style tag
      const { scope } = attrs
      return `
      /* Scope: ${ scope } */
      ${ raw }
      `
    }
  ]
})

function MyTransformScript({ html }) {
  return html`
<style scope="component">
  :host {
    display: block;
  }
</style>
<h1>My Transform Script</h1>
<script type=module>
  class MyTransformScript extends HTMLElement {
    constructor() {
      super()
    }
  }
  customElements.define('my-transform-script', MyTransformScript)
</script>
  `
}

console.log(html`<my-transform-script></my-transform-script>`)

P.S. Enhance works really well with Architect.

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Package last updated on 10 Jun 2022

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