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How to get user's list in firebase auth

I am working on the vue-firebase application and want to know that how can I get the list of all registered users in firebase auth.

I am quite not sure if that is possible with one user try to get all the users, unless you are using firebase-admin. Though I have an idea how you can do that if you trying to get a list of added user being another user.
So, try to keep another list when a new user logs in, add the user details to a new node like userList.
And when ever you need them, call that node.
And incase you are using firebase-admin
admin.auth().listUsers(1000, nextPageToken)
.then(function(listUsersResult) {
will give the list.
Here's a reference. https://firebase.google.com/docs/auth/admin/manage-users#list_all_users

Can I Send a Web Notification on a Specific Time?

I am trying to implement notifications that do not need the interaction of the backend to be shown. The use of this is to put a remind me button, that would send a notification on certain time of the day (that the user specified). I am pretty new to service workers but I understand that they work asynchronously. That being said, is there any way in which I could do something like the following pseudocode?
function timeLeft(time){
setTimeout(() => showNotification(), time);
}
This would work if I put it on a regular javascript file and the user has the browser still open.
It does not need to be exactly like that, it just needs to solve my problem. Thank you un advance.

First you need to have an ID for each browser. If you use the Push API, then you can use the browser endpoint.
When a user adds a reminder, you must store the tuple (endpoint, send_at, reminder) in your database on your server
Run a cron job on your server (or create a scheduled job with Sidekiq, etc.) in order to send the reminder at the correct time (using the Push API)
Otherwise you can use a service which allows you to create scheduled notifications: see this example on my blog.

DB structure to handle chat groups similar to Telegram/FB Messenger

Currently doing a chat app where a user could join multiple chat groups, something similar to what Telegram and Facebook Messenger has. Pretty straight forward. We're mainly using Firebase database for storing the chat groups and message details.
Sample DB structure:
To only get the chat groups a user has:
root/
users/
chatGroups/
$uid/
$chatGroupId: true
We then get the details of the chat group from a different node, same with the latest chat message in that group:
root/
chatGroups/
entries/
$groupId/
group details here...
messages/
$groupId/
$messageId/
message details here..
Everything above to get the data for a single group item that looks something like this:
All works fine. We initially get at most 5 chat groups at first, then just sort the list. The problem lies where we have to listen for updates for the chat groups -- group with the most recent chat message would go to top of the list.
The structure we have listens only to the list of groups the specific user has -- we could detect groups joined (onChildAdded) and left (onChildRemoved) by the user, but it doesn't contain the timestamp we need to sort the chat group list by the most recent changes timestamp.
Has anyone tried this similar behavior with Firebase before (we're doing a client for both Android and Web -- Javascript)? Any ideas or suggestions would be appreciated. Let me know if you need some relevant details to make things clearer.

Because there is no auto-created metadata in Firebase about when a child was added, updated or deleted and also because those operations doesn't contain the information you are searching for, you need to create your own mechanism by adding the local timestamp for each operation or by writing a server-side timestamp.
There is another approach in which you can use denormalization. Add those chats to a new created section named uxChats. The chats will need to contain only the text message and the timestamp. If you are using FirebaseUI then you can reverse the order just using this lines of code:
LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
layoutManager.setReverseLayout(true);
layoutManager.setStackFromEnd(true);
recyclerView.setLayoutManager(layoutManager)
Latest chat goes on top.
Hope it helps AL.

Parse master key cloud code following users

I'm building a simple social network app for iOS with parse and I'm currently working on the relationships, such as follower and following. I have follower and following column in my data browser saved as an array so I can save all the usernames. So this is what I'm having trouble with: Say the current user is viewing a user's profile and clicks follow I need to have the current user's name save in the follower array of the user he/she is viewing. Now as far as I know I can't o this on the client side, and it isn't a good idea anyway for security reasons to do ether. So I want to try to use the Master Key and cloud code to add each of the user's names to their appropriate array. I have never used cloud code before and I want to make sure that this is the best way to do this. I set up the Cloud Code I just don't know where to begin. Any suggestions would be appreciated!

I would start by creating a new function in main.js in your cloud code folder. Just insert the Parse.Cloud.useMasterKey(); part at the beginning. I would send up the object id of the user you are modifying, then in the function grab the array from that user, and add the current user to it. Then save and send back a success variable.
To call this from Xcode you would have something like this:
[PFCloud callFunctionInBackground:#"editFollowers" withParameters:#{#"user": Put objectId for user here}
block:^(NSString *response, NSError *error) {
if (!error) {
}
}];

Adding couchdb persistence to a socketio json feed in node

I'm currently researching how to add persistence to a realtime twitter json feed in node.
I've got my stream setup, it's broadcasting to the client, but how do i go about storing this data in a json database such as couchdb, so i can access the stores json when the client first visits the page?
I can't seem to get my head around couchdb.
var array = {
"tweet_id": tweet.id,
"screen_name": tweet.user.screen_name,
"text" : tweet.text,
"profile_image_url" : tweet.user.profile_image_url
};
db.saveDoc('tweet', strencode(array), function(er, ok) {
if (er) throw new Error(JSON.stringify(er));
util.puts('Saved my first doc to the couch!');
});
db.allDocs(function(er, doc) {
if (er) throw new Error(JSON.stringify(er));
//client.send(JSON.stringify(doc));
console.log(JSON.stringify(doc));
util.puts('Fetched my new doc from couch:');
});
These are the two snippets i'm using to try and save / retrieve tweet data. The array is one individual tweet, and needs to be saved to couch each time a new tweet is received.
I don't understand the id part of saveDoc - when i make it unique, db.allDocs only lists ID's and not the content of each doc in the database - and when it's not unique, it fails after the first db entry.
Can someone kindly explain the correct way to save and retrieve this type of json data to couchdb?
I basically want to to load the entire database when the client first views the page. (The database will have less than 100 entries)
Cheers.

You need to insert the documents in the database. You can do this by inserting the JSON that comes from the twitter API or you can insert one status at a time (for loop)
You should create a view that exposes that information. If you saved the JSON directly from Twitter you are going to need to emit several times in your map function
There operations (ingestion and querying) are not the same thing, so you should really do them at the different times in your program.
You should consider running a bg process (maybe in something as simple as a setInterval) that updates your database. Or you can use something like clarinet (http://github.com/dscape/clarinet) to parse the Twitter streaming API directly.
I'm the author of nano, and here is one of the tests that does most of what you need:
https://github.com/dscape/nano/blob/master/tests/view/query.js
For the actual query semantics and for you learn a bit more of how CouchDB works I would suggest you read:
http://guide.couchdb.org/editions/1/en/index.html
I you find it useful I would suggest you buy the book :)

If you want to use a module to interact with CouchDB I would suggest cradle or nano.
You can also use the default http module you find in Node.js to make requests to CouchDB. The down-side is that the default http module tends to be a little verbose. There are alternatives that give you an better API to deal with http requests. The request is really popular.
To get data you need to make a GET request to a view you can find more information here. If you want to create a document you have to use PUT request to your database.