constructor(options) {
    this._options = options;
    this._integrations = {};
    this._integrationsInitialized = false;
    this._numProcessing = 0;
    this._outcomes = {};
    this._hooks = {};
    this._eventProcessors = [];

    if (options.dsn) {
      this._dsn = utils.makeDsn(options.dsn);
    } else {
      debugBuild.DEBUG_BUILD && utils.logger.warn('No DSN provided, client will not send events.');
    }

    if (this._dsn) {
      const url = api.getEnvelopeEndpointWithUrlEncodedAuth(this._dsn, options);
      this._transport = options.transport({
        tunnel: this._options.tunnel,
        recordDroppedEvent: this.recordDroppedEvent.bind(this),
        ...options.transportOptions,
        url,
      });
    }
  }
Initializes this client instance.

@param options Options for the client.