
@popeindustries/lit-html
Seamlessly and efficiently use @popeindustries/lit-html-server rendered HTML to hydrate lit-html templates in the browser.
Features
- seamless hydration: first call to
render()
will hydrate if possible, with subsequent calls updating the existing DOM by forwarding to lit-html.render()
. - hydration errors will cause the server rendered markup to be cleared and replaced with the result of
lit-html.render()
. - render multiple sub-trees in the same container.
- easily enable lazy (partial/deferred) web component hydration with
lazy-hydration-mixin
and hydrate:idle
or hydrate:visible
attributes.
Usage
Install with npm/yarn/pnpm
:
$ npm install --save @popeindustries/lit-html
Given the following server rendered HTML:
<body>
<h1>Some Title</h1>
<nav negative>
<button>one</button
><button>two</button
><button>three</button
>
</nav>
<p>
Some paragraph of text to show that multiple<br />
hydration sub-trees can exist in the same container.
</p>
<main>This is the main page content.</main>
<footer>Some footer</footer>
</body>
...import your lit-html templates used on the server:
import { html } from '@popeindustries/lit-html';
function renderMenu(data) {
const { negative, sections } = data;
return html`<nav ?negative="${negative}">${sections.map((section) => html`<button>${section}</button>`)}</nav>`;
}
function renderPage(data) {
return html`<main>This is the main page content.</main>`;
}
...and render:
import { render } from '@popeindustries/lit-html';
render(renderMenu(data), document.body, { renderBefore: document.querySelector('body > p') });
render(renderPage(data), document.body, { renderBefore: document.querySelector('body > footer') });
Note
Due to how the lit*
family of packages are minified and mangled for production, the @popeindustries/lit-html
package is forced to vendor the lit-html
package. This shouldn't affect normal use as long as application code does not mix imports from @popeindustries/lit-html
and lit-html
.
lazy-hydration-mixin
When hydrating sub-trees containing nested web components, it is often necessary to control the hydration order to allow parent elements to pass data down to their children. When rendering web components on the server, lit-html-server adds a hydrate:defer
attribute that may be used to determine when hydration should take place.
The lazy-hydration-mixin
is an easy way to add support for basic hydration deferral by delaying the call to the base class's connectedCallback()
method:
import { html, render } from '@popeindustries/lit-html';
import { lazyHydrationMixin } from '@popeindustries/lit-html/lazy-hydration-mixin.js';
class MyBaseClass extends HTMLElement {
connectedCallback() {
render(this.render(), this, { host: this });
}
}
class MyEl extends lazyHydrationMixin(MyBaseClass) {
connectedCallback() {
super.connectedCallback();
}
render() {
return html`<span>some content</span>`;
}
}
This simple mechanism also enables additional forms of deferral, and the lazy-hydration-mixin
includes two additional strategies:
hydrate:idle
Adding the hydrate:idle
attribute to the element waits until the browser has performed any pending high priority work before hydrating the element (requires the requestIdleCallback
API, otherwise it falls back to default behaviour):
<my-el hydrate:idle></my-el>
hydrate:visible
Adding the hydrate:visible
attribute to the element waits until the element is visible in the viewport before hydrating the element (requires the IntersectionObserver
API, otherwise it falls back to default behaviour).
<my-el hydrate:visible></my-el>