Cordova SQLite: database already open: data.db - sqlite

Question

I am trying to implement a chat app in Ionic 2 and I use SQLite.
I am however, getting the following error when I execute a executeSql on the database.
TypeError {stack: (...), message: "Cannot read property 'executeSql'
of undefined"}
But when I open the databse each transaction, I don't get the above error, but get the following warning:
database already open: data.db
I have been reading the Ionic and Cordova documentation, but cannot seem to understand what I am doing incorrect. If anyone can advise, I would appreciate it.
chatsStorageService.ts
public openDatabase(): Promise<Array<Message>> {
let promise: Promise<Array<Message>> = new Promise<Array<Message>>(resolve => {
console.log('openDatabase: ', this.database);
if (this.database && this.database != null) {
return Promise.all([this.refreshChats(this.database), this.refreshMessages(this.database)]).then(() => {
resolve(this.messages);
});
} else {
this.database = new SQLite();
this.database.openDatabase({
name: "data.db",
location: "default"
}).then(() => {
return Promise.all([this.refreshChats(this.database), this.refreshMessages(this.database)]).then(() => {
resolve(this.messages);
});
}, (error) => {
console.log("OPEN ERROR: ", error);
});
}
});
return promise;
}
public refreshChats(db: any): Promise<Array<Chat>> {
let promise: Promise<Array<Chat>> = new Promise<Array<Chat>>(resolve => {
return db.executeSql("SELECT * FROM chats", [])
.then((chatData) => {
let promises: Array<any> = [];
this.chats = [];
if (chatData.rows.length > 0) {
for (var i = 0; i < chatData.rows.length; i++) {
promises.push(this.populateChat(db, chatData.rows.item(i)));
}
}
return Promise.all(promises).then(() => {
resolve(this.chats);
});
})
.catch(error => {
console.log("ERROR REFRESHING CHATS: " + JSON.stringify(error));
console.log(error);
});
});
return promise;
}