Server side render for Custom Elements.
Enhance enables a web standards based workflow that embraces the platform by supporting Custom Elements and slot syntax.
npm i @enhance/ssr
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>`)Elements are pure functions that are passed an object containing an html function used to expand custom elements and a state object comprised of attrs which are the attributes set on the custom element and a store object that contains application state.
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>
`
}The rendered output
<head>
<style scope="global">
h1 {
color: red;
}
</style>
</head>
<body>
<hello-world>
<h1>Hello World</h1>
</hello-world>
</body>You can also use an object that exposes a render function as your template. The render function will be passed the same arguments { html:function, state:object }.
{
attrs: [ 'label' ],
init(el) {
el.addEventListener('click', el.click)
},
render({ html, state }) {
const { attrs={} } = state
const { label='Nope' } = attrs
return html`
<pre>
${JSON.stringify(state)}
</pre>
<button>${ label }</button>
`
},
click(e) {
console.log('CLICKED')
},
adopted() {
console.log('ADOPTED')
},
connected() {
console.log('CONNECTED')
},
disconnected() {
console.log('DISCONNECTED')
}
}Use these options objects with the enhance custom element factory
Supply initital state to enhance and it will be passed along in a store object nested inside the state object.
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>`)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>
`
}The store is used to pass state to all components in the tree.
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>Enhance supports unnamed slots for when you want to create a container element for all non-slotted child nodes.
export default function MyButton({ html }) {
return html`
<button>
<slot>Submit</slot>
</button>
`
}<my-button></my-button>
<my-button>Save</my-button>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 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 } */
${ raw }
`
}
]
})
function MyTransformScript({ html }) {
return html`
<style scope="component">
:host {
display: block;
}
</style>
<h1>My Transform Script</h1>
<script type=module>
class MyTransformScript extends HTMLElement {
constructor() {
super()
}
}
customElements.define('my-transform-script', MyTransformScript)
</script>
`
}
console.log(html`<my-transform-script></my-transform-script>`)Enhance SSR outputs an entire valid HTML page but you can pass bodyContent: true to get the content of the body element. This can be useful for when you want to isolate output HTML to only the Custom Element you are authoring.
const html = enhance({
bodyContent: true,
elements: {
'my-paragraph': MyParagraph,
}
})
const output = html`
<my-paragraph></my-paragraph>
`There are times you will need to pass state to nested child custom elements. To avoid the tedium of passing attributes through multiple levels of nested elements Enhance SSR supplies a context object to add state to.
Parent sets context
export default function MyContextParent({ html, state }) {
const { attrs, context } = state
const { message } = attrs
context.message = message
return html`
<slot></slot>
`
}Child retrieves state from parent supplied context
export default function MyContextChild({ html, state }) {
const { context } = state
const { message } = context
return html`
<span>${ message }</span>
`
}Authoring
<my-context-parent message="hmmm">
<div>
<span>
<my-context-child></my-context-child>
</span>
</div>
</my-context-parent>When rendering custom elements from a single template there are times where you may need to target a specific instance. The instanceID is passed in the state object.
export default function MyInstanceID({ html, state }) {
const { instanceID='' } = state
return html`
<p>${instanceID}</p>
`
}P.S. Enhance works really well with Begin.