lit-signals-helpers

Set of helpers on top of @lit-labs/preact-signals

Decorator

If you prefer a decorator over a mixin, you can use @signalable:

1import {signalable, signal} from 'lit-signals-helpers';
2
3const $username = signal('John Doe');
4
5@customElement('my-element')
6@signalable
7class E extends LitElement {
8	// Called every time $username changes.
9	render() {
10		return html`
11			<p>Hello ${$username}</p>
12
13			<button @click=${this.#signout}>signout</button>
14		`;
15	}
16
17	#signout() {
18		$username.value = 'anonymous';
19	}
20}

Note: when a signal value changes it will update all the views that depends on it as long as views use @signalable of course.

html tagged template

Unmodified html tagged template from the @lit-labs/preact-signals package. The advantage of this tag over the decorator is that when a signal changes it will only update the DOM part that depends on it and do not request a complete update from the Lit element.

1import {html, signal} from 'lit-signals-helpers';
2
3const $username = signal('John Doe');
4
5@customElement('my-element')
6class E extends LitElement {
7	render() {
8		return html`Hello <b>${$username}</b>`;
9	}
10}

When $username changes somewhere, <b> content is automatically updated with the new value.

Local storage support

If you would like to persist your signal values between page refreshes, you can use this module.

Here's an example:

1import {lsignal} from 'lit-signals-helpers';
2
3export const $userName = lsignal('userstore', 'name', 'anonymous');
4export const $useAge = lsignal('userstore', 'age', 0);

or using compound syntax

1import {compound} from 'lit-signals-helpers';
2
3// Using compound syntax improves readability.
4
5const c = compound('userstore');
6
7export const $userName = c.signal('name', 'anonymous');
8export const $userAge = c.signal('age', 0);
9
10// You can access all the compound signals for debugging purpose.
11console.log(c.signals);
12// Though Intellisense is unaware of the following type
13// you can access and use a signal directly from the compound.
14c.signals.$userName.value = 'John Doe';
15
16// Export for general use.
17export const userCompound = c;