NodeJS: WebSocket Client (Browser-compatible)

WsClient.js

/*
 websocket client module (supports either NodeJS and browser)
 
 NOTE:
`browserify` makes this websocket client lib browser-compatible.
 
 # Usage
 ```
const onmessage = function(e) {
  console.log("onmessage:", e);
};

(async() => {
  // new instance:
  const client = new WsClient({
    url: "wss://...",
  });
  // open:
  const e = await client.open(onmessage); // callback also available: `client.open(onmessage, (e) => { // connected! });`
  const param = {
    "hello": "world"
  };
  // send:
  client.send(param);
})().catch(console.error);
 ```
*/
const WebSocket = require('websocket').w3cwebsocket; // browser compatible websocket module

module.exports = class WsClient {

  constructor({
    url,
    debug = false,
    logger = console,
  }) {
    const self = this;
    if (!WsClient.isValidUrl(url))
      throw Error(`invalid url: "${url}"`);
    this.url = url;
    this.debug = debug;
    this.logger = logger;
  }

  async open(onmessage, cb) {
    const self = this;
    this.client = new WebSocket(this.url);
    this.client.onmessage = onmessage;
    if (typeof cb === "function") { //callback
      this.client.onopen = function(e) {
        return cb && cb(e);
      };
    } else { // async/await
      return new Promise(function(resolve, reject) {
        self.client.onopen = function(e) {
          resolve(e);
        };
        self.client.onerror = function(err) {
          reject(err);
        };
      });
    }
  }

  close() {
    this.client.close();
  }

  send(param) {
    const self = this;
    if (!self.client) {
      throw Error("ws client not connected yet.");
    }
    if (typeof param !== "string") {
      param = JSON.stringify(param);
    }
    this.client.send(param);
  }

  //**************************************************************
  // utility static methods
  //**************************************************************

  static isValidUrl(v) {
    return /^wss?:\/\/.+$/.test(v);
  }

};