Exciting news!Announcing our $4.6M Series Seed. Learn more
Socket
LoveBlogFAQ
Install
Log in

wc-context

Package Overview
Dependencies
0
Maintainers
1
Versions
17
Issues
File Explorer

Advanced tools

wc-context

Context for HTML custom elements / web components

    0.10.0latest

Version published
Maintainers
1
Yearly downloads
19,399
decreased by-5.21%

Weekly downloads

Readme

Source

wc-context

A context implementation for web components

Features

    ✓ Small, fast and flexible
    ✓ No need to dedicated "provider" or "consumer" elements
    ✓ Ability to provide or consume one or more contexts per element
    ✓ Context can be provided or consumed by any HTML element
    ✓ Context can be identified by string or unique identifier
    ✓ Easy to implement unit tests (same as components without context)
    ✓ Builtin integration with LitElement
    ✓ Builtin ContextProvider class with primitives for lazy loading
    ✓ No Internet Explorer support

Live examples

  • lit: version 1 / version 2

Lit integration

The easiest way to use wc-context is with the Lit integration exported in the lit namespace (wc-context/lit). It provides a withContext class mixin that hooks into the property reactivity system allowing to define context using the property declaration. The context is automatically propagated when the property is updated.

See below for the generic implementation that works with any web component, declared with library or not.

Providing a context

To provide a context add providedContext to the property declaration

import { withContext } from 'wc-context/lit' import { LitElement } from 'lit' class Provider extends withContext(LitElement) { static properties = { value: { type: String, providedContext: 'theme' }, activeTitle: { type: String, providedContext: 'title' }, } toggleTheme() { this.value = 'newtheme' } toggleTitle() { this.activeTitle = 'New title' } }

Consuming a context

To consume a context add context to the property declaration

import { withContext } from 'wc-context/lit' import { LitElement, html } from 'lit' class Consumer extends withContext(LitElement) { static properties = { theme: { type: String, context: 'theme' }, titleProp: { type: String, context: 'title' }, } render() { return html`<div>Theme is ${this.theme}, title is ${this.titleProp}</div>` } }

Generic implementation

The withContext class mixin exported in the root namespace, implements an API similar to DOM observedAttributes/attributeChangedCallback.

Contexts are defined in an custom element through static providedContexts field where the key is the context name and value holds a configuration object. The configuration can have a value property defining the default context value or a property one defining from what component property the context will retrieve its value.

Providing a context

import { withContext } from 'wc-context' class Provider extends withContext(HTMLElement) { static providedContexts = { theme: { value: 'blue' }, title: 'activeTitle', // shorthand for { property: 'activeTitle' } } get activeTitle() { return this._activeTitle } set activeTitle(value) { this._activeTitle = value this.updateContext('title') } toggleTheme() { this.updateContext('theme', 'newtheme') } toggleTitle() { this.activeTitle = 'New title' } }

Consuming a context

import { withContext } from 'wc-context' class Consumer extends withContext(HTMLElement) { static observedContexts = ['theme', ['title', 'titleProp']] contextChangedCallback(name, oldValue, value) { console.log(`theme changed from "${oldValue}" to "${value}"`) // updates el accordingly } connectedCallback() { super.connectedCallback() this.innerHTML = `<div>Theme is ${this.theme}, title is ${this.titleProp}</div>` } }

Low level API

wc-context also exports its low level functions that can be used to handle specific cases or create a new interface as for example generic provider and consumer elements implemented below.

import { registerContext, updateContext, observeContext, unobserveContext, } from 'wc-context/core' // custom element that publishes an arbitrary context name and value function getFromProperty(provider, prop) { return provider[prop] } class ContextProvider extends HTMLElement { static get observedAttributes() { return ['name', 'value'] } get name() { return this._name } set name(value) { if (!this._name && value) { // register context once registerContext(this, this.name, 'value', getFromProperty) } this._name = value } attributeChangedCallback(name, oldValue, value) { this[name] = value } set value(val) { this._value = val if (this.name) { updateContext(this, this.name) } } get value() { return this._value } } customElements.define('context-provider', ContextProvider) class ContextUpdateEvent extends Event { constructor(context, value) { super('context-update', { bubbles: true }) this.context = context this.value = value } } function setValueDispatchEvent(consumer, value, context) { consumer.value = value consumer.dispatchEvent(new ContextUpdateEvent(context, value)) } class ContextConsumer extends HTMLElement { static get observedAttributes() { return ['name'] } attributeChangedCallback(name, oldValue, value) { this[name] = value } connectedCallback() { this._context = this.name if (this._context) { observeContext(this, this._context, this._context, setValueDispatchEvent) } } disconnectedCallback() { if (this._context) { unobserveContext(this, this._context) } } } customElements.define('context-consumer', ContextConsumer) // later document.body.innerHTML = ` <context-provider name="theme" value="light"> <div> <context-consumer name="theme"></context-consumer> </div> </context-provider>` const provider = document.querySelector('context-provider') const consumer = document.querySelector('context-consumer') consumer.addEventListener('context-update', ({ context, value }) => { console.log(`Context ${context}:${value}`) }) provider.value = 'dark'

License

MIT Copyright © 2021 Luiz Américo Pereira Câmara

Keywords

Socket

Product

Subscribe to our newsletter

Get open source security insights delivered straight into your inbox. Be the first to learn about new features and product updates.


  • Terms
  • Privacy
  • Security

Made with ⚡️ by Socket Inc