Method on

examples/basic-websocket-client/src/index.js:4–10

(event, listener)

  #listeners = new Map();

  on(event, listener) {
    let listeners = this.#listeners.get(event);
    if (!listeners) {
      this.#listeners.set(event, (listeners = []));
    }
    listeners.push(listener);
  }

  emit(event, ...args) {
    const listeners = this.#listeners.get(event);