restSendTx.ts

  public async sendRestTransaction(
    serializedTx: Uint8Array | Buffer | Array<number>,
    retries,
    rpcEndpoint = this.defaultConnection.rpcEndpoint,
    skipPreFlight = true
  ): Promise<TransactionSignature> {
      const res = await fetch(rpcEndpoint, {
        method: "POST",
        headers: {
          "Content-Type": "application/json",
        },
        body: JSON.stringify({
          jsonrpc: "2.0",
          id: Math.round(Math.random() * 1_000_000),
          method: "sendTransaction",
          params: [
            serializedTx!.toString("base64"),
            {
              skipPreflight: skipPreFlight,
              encoding: "base64",
              maxRetries: retries,
            },
          ],
        }),
      });
      return ((await res.json()) as any)!.result!;
  }