import { html, css, LitElement } from 'https://unpkg.com/lit-element/lit-element.js?module'; export class WebsocketConnection extends LitElement { static get styles() { return css``; } static get properties() { return { url: { type: String } } } constructor() { super(); this.url = ''; this.socket = null; } onopen(event){ console.log("websocket connected"); } onclose(event){ console.log("websocket closed"); } onerror(event){ console.log("websocket error, closing..."); if (this.socket && this.socket.readyState === WebSocket.OPEN) { this.socket.close(); } } onmessage(event){ console.log("received message:", event.data); } isSocketConnected(){ if (! this.socket){ return false; } if (this.socket.readyState === WebSocket.OPEN) { return true; } return false; } sendMessage(msg){ if (this.isSocketConnected()) { var string_msg = JSON.stringify(msg); this.socket.send(string_msg); } else { console.error("cannot send message, websocket disconnected"); } } connect() { console.log(`connect to ${this.url}...`); this.socket = new WebSocket(this.url); this.socket.onopen = (event) => this.onopen(event); this.socket.onclose = (event) => this.onclose(event); this.socket.onerror = (event) => this.onerror(event); this.socket.onmessage = (event) => this.onmessage(event); } update(props) { if (props.has("url")){ this.connect(); } super.update(props); } render() { // do nothing return html``; } } customElements.define('websocket-connection', WebsocketConnection);