import {LitElement, html, css} from 'lit-element'; import {customElement, property} from 'lit/decorators.js'; @customElement('click-counter') export class ClickCounter extends LitElement { static styles = css` :host { display: block; } `; @property({type: Number}) count = 0; render() { return html` `; } private _onClick() { this.count++; } } declare global { interface HTMLElementTagNameMap { 'click-counter': ClickCounter; } }