import HyperHTMLElement from "hyperhtml-element"; class MyCounter extends HyperHTMLElement { constructor() { super(); this.attachShadow({ mode: "open" }); } created() { this.count = 0; this.render(); } inc = () => { this.count++; this.render(); }; dec = () => { this.count--; this.render(); }; render() { return this.html` ${this.count} `; } } MyCounter.define("my-counter");