Method ensureWsApiConnection

src/node-binance-api.ts:3947–3965

* Ensures a WebSocket API connection is open for the given connectionId * @param {string} connectionId - connection identifier * @return {promise} - resolves when the connection is open

(connectionId: string)

    * @return {promise} - resolves when the connection is open
    */
    private ensureWsApiConnection(connectionId: string): Promise<void> {
        return new Promise((resolve, reject) => {
            const existing = this.wsApiConnections[connectionId];
            if (existing) {
                if (existing.readyState === WebSocket.OPEN) {
                    resolve();
                    return;
                }
                if (existing.readyState === WebSocket.CONNECTING) {
                    existing.once('open', () => resolve());
                    existing.once('error', (err: Error) => reject(err));
                    return;
                }
            }
            const ws = this.connectWsApi(connectionId, () => {}, () => {});
            ws.once('open', () => resolve());
            ws.once('error', (err: Error) => reject(err));
        });
    }

    /**
    * Gets the book tickers of given symbol(s)