Lit-element-simple-context NPM

lit-element-context state manager

It supposed to be a simple context provider but somehow it became a store 🪦

It's a simple state manager for lit-element. I needed something like redux, but something less complicated. It implements a store, and provides a method to set and update properties in the store.

On every property update, the components get a new data injected into them through props, and as we know, components are rerendered if the properties are changed.

you can find a working example in the test/components folder.

New features

Version 1.2.5

changed "module" to "ES6"

Version 1.2.1

added generic types for state

Version 1.2.0

added TS support for lit-ts

Version 1.1.1

improved redux devtools usage

Version 1.1.0

removed deprecated methods
improved register and deregister methods on lifecycle
remove component from observers when disconnected from DOM

Version 1.0.13

added meta information to the store init method

Version 1.0.12

added iframe support

Version 1.0.11

added devtools support

Version 1.0.9

rename prop with contextKey attribute

Version 1.0.6

fromContext attribute in the properties getter

Version 1.0.5

actions and async actions
setProps method to set multiple values at the same time

Usage

init the context where ever you want

import context from 'lit-element-simple-context';

context.init({propName: someval, propName2: {nestedData: []} });

You can use devtools to debug store, pass true as a second parameter to the init method.

import context from 'lit-element-simple-context';

context.init({...}, true);

You can pass devtools options, like store instance name, as third parameter to the init method. Watch devtools-options.d.ts for available options.

import context from 'lit-element-simple-context';

context.init({...}, true, { name: 'lit context store' });

connect a lit component to the context in JS

import { LitElement } from 'lit';
import context from 'lit-element-simple-context';

class MyLitComponent extends LitElement {}

window.customElements.define('my-lit-component', context.connect(MyLitComponent));

connect a lit component to the context in TS

import { LitElement, property } from 'lit';
import { Context } from 'lit-element-simple-context';

type MyContextType = {};
const context = new Context<MyContextType>();

@customElement('my-lit-component')
@context.connectElement()
export class MyLitComponent extends LitElement {}

To specify the props you need from context in your component, you should set fromContext attribute in the properties getter. If the lit property name is different what you use in the store, you can specify it with contextKey attribute

class MyLitComponent extends LitElement {
  static get properties() {
    return {
      somepropFromContext: {type: Number, fromContext: true},
      renamedProp: {type: String, fromContext: true, contextKey: 'somepropInTheStore'}
    }
  }
}

You can do it in TS as well with either using the default typings or your custom state type:

import { LitElement } from 'lit';
import context from 'lit-element-simple-context';

@customElement('my-lit-component')
@context.connectElement()
export class MyLitComponent extends LitElement {

  @property({fromContext: true})
  somepropFromContext = '';
  
}

With custom types:

import { LitElement, property } from 'lit';
import { Context } from 'lit-element-simple-context';

type MyContextType = {};
const context = new Context<MyContextType>();

@customElement('my-lit-component')
@context.connectElement()
export class MyLitComponent extends LitElement {

  @property({fromContext: true})
  somepropFromContext = '';
  
}

change a value in the store once the component is connected to the store

this.setProp('somepropFromContext2', 0);

change a value in the store if the component is not connected to the store

import context from 'lit-element-simple-context';

context.setProp('someprop', context.state.someprop + 1);

You can use actions (and async actions as well) instead of setProp method calls.

// actions.js
import context from 'lit-element-simple-context';

export const incrementBy = context.action((state, value) => ({someprop: state.someprop + value}));

export const asyncAction = context.asyncAction(async (_, value1, value2) => ({ value1, value2}));


// some-other-file.js
import { asyncAction, incrementBy } from './actions.js';

async function foo() {
  await asyncAction('foo', 'bar');

  incrementBy(1);
}

that's it!! there is no need of tons of boilerplate code and every component gets the fresh data on change.