Get the current account or set it if there is no current account

currentAccount.ts

/** Get the current account */
public currentAccount(): Observable<string | Error> {
    if (this.web3.eth.defaultAccount) {
        return of(this.web3.eth.defaultAccount);
    } else {
        return this.getAccounts().pipe(
            tap((accounts: string[]) => {
                if (accounts.length === 0) { throw new Error('No accounts available'); }
            }),
            map((accounts: string[]) => accounts[0]),
            tap((account: string) => this.web3.eth.defaultAccount = account),
            catchError((err: Error) => of(err))
        );
    }
}