Web component server-side rendering and testing


This repo contains all you need to server-side render your web components and
run their tests in a node environment.

* Uses undom for a minimal DOM API in
Node.
* Great for rendering out static sites from components.
* Run your tests in Jest!
* Statically generate JS files to HTML files.

Installing

``
npm install @skatejs/ssr
`

Usage

_This example is using vanilla custom elements and shadow DOM in order to show
that it can work with any web component library._

On the server (example.js):

`js
require('@skatejs/ssr/register');
const render = require('@skatejs/ssr');

class Hello extends HTMLElement {
connectedCallback() {
const shadowRoot = this.attachShadow({ mode: 'open' });
shadowRoot.innerHTML =
'Hello, !';
}
}
class Yell extends HTMLElement {
connectedCallback() {
Promise.resolve().then(() => {
const shadowRoot = this.attachShadow({ mode: 'open' });
shadowRoot.innerHTML = '';
});
}
}
customElements.define('x-hello', Hello);
customElements.define('x-yell', Yell);

const hello = new Hello();
hello.textContent = 'World';

render(hello).then(console.log);
`

And then just node your server code:

`
$ node example.js
Hello, !World
`

On the client, just inline your server-rendered string:

`html
Hello, !World
`

See it in action!

API

The only function this library exposes is render(). The first argument is the
DOM tree you want to render. It can be a document node or any HTML node. The
second argument are the options to customise rendering. These options are:

* debug - Whether or not to pretty print the HTML result. Defaults to false.
* rehydrate - Whether or not to add the inline rehydration scripts. Defaults
to true.
* resolver - The function to call that will resolve the promise. Defaults to
setTimeout.

Running in Node

If you want to run your code in Node, just require the registered environment
before doing anything DOMish.

`js
// index.js
require('@skatejs/ssr/register');

// DOM stuff...
`

Running in Jest

If you want to run your tests in Jest, all you have to do is configure Jest to
use the environment we've provided for it.

`js
// package.json
{
"jest": {
"testEnvironment": "@skatejs/ssr/jest"
}
}
`

Static-site generation

This package ships with a command that you can use to statically generate a site
from JS files.

* It uses babel-register to parse your JS files.
* Each JS file must have a default export that is a custom element.

`sh
ssr --out public --src path/to/site/*/.js
`

Options are:

* --babel - Path to custom babel config. Uses require() to load relative to
process.cwd(). Defaults to .babelrc / package.json field.
* --debug - Whether or not to pretty print the HTML result. Defaults to
false.
* --out - The directory to place the statically rendered files.
* --props - A JSON object of custom props to assign to the custom elements
before they're rendered.
* --rehydrate - Whether or not to add rehydration scripts. Defaults to true.
* --src - A glob for the source files to statically render to --out.
* --suffix - The suffix to put on the output files. Defaults to html;

$3

You can use something like nodemon to watch for updates and then regenerate
your site:

`sh
nodemon --exec "ssr --out public --src path/to/site/*/.js" --watch path/to/site
`

Running with other Node / DOM implementations

There's other implementations out there such as
Domino and
JSDOM. They don't yet have support for custom
elements or shadow DOM, but if they did, then you would use this library in the
same way, just without requiring @skatejs/ssr/register. With some
implementations that don't yet support web components, requiring
@skatejs/ssr/register may work, but your mileage may vary. Currently only
Undom is officially supported.

The future

The definition of success for this library is if it can be made mostly
redundant. Things like a DOM implementation in Node (JSDOM / UnDOM, etc) are
still necessary. The static-site generation will probably still be a thing.
However, we hope that the serialisation and rehydration of Shadow DOM can be
spec'd - in some way - and a standardised API for doing so makes it's way to the
platform.

Serialisation may still be done in a Node DOM implementation, but it'd be great
to see it standardised beacuse it is tightly coupled to the rehydration step on
the client. This also helps to ensure that if an imperative distrubution API
ever makes its way into the spec, that both serialisation and rehydration may be
accounted for.

Notes

There's some notes and limitations that you should be aware of.

$3

Scoped styles are emulated by scoping class names only. This means you are
limited to using only class names within your shadow root
`

It will make that class name unique and scope it to the shadow roots that use
it.

Support for both :host and :slotted still need to be implemented.

Style tags are also deduped. This means that if you use a