README.md

lit-element

Base class for creating custom elements using Polymer and lit-html.

import {LitElement, html} from 'node_modules/@polymer/lit-element/lit-element.js'

class MyElement extends LitElement {

  // Public property API that triggers re-render (synched with attributes)
  static get properties() {
    return {
      foo: String,
      whales: Number
    }
  }

  constructor() {
    super();
    this.foo = 'foo';
  }

  ready() {
    this.addEventListener('click', async (e) => {
      this.whales++;
      await this.nextRendered;
      this.dispatchEvent(new CustomEvent('whales', {detail: {whales: this.whales}}))
    });
    super.ready();
  }

  // Render method should return a `TemplateResult` using the provided lit-html `html` tag function
  render({foo, whales}) {
    return html`
      <style>
        :host {
          display: block;
        }
      </style>
      <h4>Foo: ${foo}</h4>
      <div>whales: ${'🐳'.repeat(whales)}</div>
      <slot></slot>
    `;
  }

}
customElements.define('my-element', MyElement);

  <my-element whales="5">hi</my-element>

Known Issues

• This element does not yet work with the ShadyCSS polyfill. Support is coming soon!
• API is subject to minor changes.
• See lit-html for more info.