praneshr / lit-element

A simple base class for creating fast, lightweight web components

LitElement

A simple base class for creating fast, lightweight web components with lit-html.

Documentation

Full documentation is available at lit-element.polymer-project.org.

Overview

LitElement uses lit-html to render into the element's Shadow DOM and adds API to help manage element properties and attributes. LitElement reacts to changes in properties and renders declaratively using lit-html. See the lit-html guide for additional information on how to create templates for lit-element.

    import {LitElement, html, css, customElement, property} from 'lit-element';

    // This decorator defines the element.
    @customElement('my-element')
    export class MyElement extends LitElement {

      // This decorator creates a property accessor that triggers rendering and
      // an observed attribute.
      @property()
      mood = 'great';

      static styles = css`
        span {
          color: green;
        }`;

      // Render element DOM by returning a `lit-html` template.
      render() {
        return html`Web Components are <span>${this.mood}</span>!`;
      }

    }

    <my-element mood="awesome"></my-element>

Note, this example uses decorators to create properties. Decorators are a proposed standard currently available in TypeScript or Babel. LitElement also supports a vanilla JavaScript method of declaring reactive properties.

Examples

• Runs in all supported browsers: Glitch

• Runs in browsers with JavaScript Modules: Stackblitz, JSFiddle, JSBin, CodePen.

• You can also copy this HTML file into a local file and run it in any browser that supports JavaScript Modules.

Installation

From inside your project folder, run:

$ npm install lit-element

To install the web components polyfills needed for older browsers:

$ npm i -D @webcomponents/webcomponentsjs

Supported Browsers

The last 2 versions of all modern browsers are supported, including Chrome, Safari, Opera, Firefox, Edge. In addition, Internet Explorer 11 is also supported.

Edge and Internet Explorer 11 require the web components polyfills.

Contributing

Please see CONTRIBUTING.md.