I have a small Node.js HTTP server that does requests to a mongo database (with the mongoose module).
What I want to do is query the database, store it in a variable (array) and send it to the client.
Because ideally, when the user clicks on one of the buttons on the html page, the JavaScript will pick-up the event and change the appearance of the website by showing calculations based on data that is stored in the database.
The only way I could come with was just "transferring" the database content to the client browser but if anyone can come with another solution that would be fine too !
So basically my question is :
How can I pass a variable from the Node.js server to the client browser when serving a page ?
Thank you in advance !
If you will be doing more than a couple of these types of transfers, I recommend looking into Socket.IO.
It's a layer that provides quick and easy communication between Node.js servers and web front-ends, by abstracting web sockets when available, and falling back to other transports (such as JSON-P or Flash) when it's not available. Basically, you would call io.emit('something', {yourdata: here}), and it is easily received on the other end. All of the serialization is done for you.
http://socket.io/
Give their demo a shot to see how it works.
Related
I want to update the HTML/pug page of multiple users when particular data changes in my MongoDB database. A user(A) follows another user(B) (whose data is stored in a different collection). When user(B) updates something, user(A) should see the change. There can be multiple people following the same user, and all the people following the user should see live updates.
I tried looking into socket.io but it doesn't look like it is the right thing for my purpose.
Your main options are either websockets (socket.io), server side push notifications with http2, or polling with http.
If socket.io seems overkill, server push notifications probably will too.
You can poll instead. Ie, send an http request from the client at regular intervals, like every 10 (or whatever seems suitable) seconds and update the page based on the response data
You’ll need to use JavaScript on the client for this. Pug templates render just once on page load. If you want dynamic updates after the initial render, you need client side JavaScript in all cases.
I'm currently working on an analytics webapp with a react frontend and node (express) backend.
Describing the functionality in a nutshell:
A user will be able to login on the website, search for a YouTube username and then the YouTube API is called, the data will be stored in a mysql db via my express API and also the data will be used to calucalte some statistics which afterwards are displayed in a dashboard.
Now I was wondering if I should:
Call the YouTube API from the frontend, i.e. inside my react code, do the calculations display them and and then store it in the DB via my express API.
Or, from the react app call an endpoint in my express API that will then call the YouTube API, store the data in the DB and then pass on the data to my react app.
Are there any best practices or up-/downsides to either approach?
When answering questions like these, it's important to remember that the client-side is different for each and every user that visits your website, their internet speed, their GPU & CPU power, etc., but the server is most commonly held in a stable container and much more powerful than a client.
The proper way would be the following:
1. Obtain a search query from a client
Meaning you should get the user's search query from an input, or any other form of control (text area, checkbox, etc.), this way client is doing the least business logic, as it should. The client should always focus more on UI / UX rather than business logic.
2. Send query to the server
Let the server use the query you've just obtained from client, call the youtube api from the server (either explicitly using Axios, or find a node.js youtube library), and do all the necessary calculation on the backend
3. Send processed data to the client
Let client receive the data in the form which is ready for use (iterations, mappings, etc.) - again separating concerns, server - business logic, client - UI / UX
Now to be fair, the example you have will most commonly be done all on the client-side, since it is not as computationally heavy as other enterprise examples, but this is a good rule to follow for big projects, and no one would really complain if you did it this way, since it would be the proper way.
Have small app (My first Node js App), where I want add changing real-time content.
For example I have a common url which have list of content link, when user click on particular link it will open its correspondence link.
I have teacher and student role in the app so if teacher open the specific content(From the common url page) then it will automatically open that content for all student who have common url.
Please give me any Idea to implement this functionality and please tell me any plugin who have same functionality for real time content change.
One way, probably the easiest would be to use websockets, an easily manageable choice is socket.io npm package. What makes websockets different from http requests is the direction of the data flow. While http is pull based, meaning that a request has to be made to the server in order to get a response, websockets - once the connection is established - are or at least can be push based, meaning that the server could push out content without having to get a request from the client. In your situation, the teacher and the studens would all have an active websocket connection with the server. When the teacher clicked on a certain view, it would push the view’s data requirements to the students without any interaction from their side and the view would update on their screens according to the pushed data.
Look into how websockets work and try to experiment with a basic socket.io setup.
I want to develop an attendance management page where I want to update my MongoDB database every time when the user leaves the page.
I found unload function in some answers, but cannot realize how to use it in Node.js.
How can I do this using Node.js framework in PhpStorm?
You would have to do it from server side, sending request from client before he leaves the page is a bad approach. There are many ways how client can disconnect without sending any request, like connection lost, killing process etc.
Maybe consider different approach, like sending an ajax request as an indication that user is still on page?
Or you could look around for existing solutions, maybe something like Using node.js to display number of current users
could help.
I already asked a similar question but this one is a bit different/specific:
I'm about to start development of a social community site (for a local user group) with features like timeline, IM/chat, forums, ...
Node.js and socket.io (or now.js) on the backend. jQuery (and maybe backbone.js or similar) on the front end. Content is loaded via socket.io or ajax and navigation via url hash.
There are 2 things where I just can't decide which way to go. I hope here are some people who can provide some good or bad experience.
Templating on server or in browser? I'm not sure if it's better to load a complete html site + live updates (also in html) for timeline, forum posts, IM/chat, ... or use something like a REST api via ajax or socket.io and do the templating on the client site. I've never done that before. You need to download the templates, etc, etc. Has anyone experience in this? There are also 2 ways to implement a rest-like api: E.g. request a forum post, then request the user associated to that post and so on (just like server side MVC) - or - request a forum post and the server answers with all needed information.
Load content via ajax or socket.io? I'm definitively using socket.io or now.js for real-time communication (IM, chat) and pubsub (on mainpage -> subscribe to new timeline updates, on a forum topic -> subscribe to new posts). But should I also load HTML (or provide a REST-like API, see question 1) through the socket? When people open forum posts in tabs (which I usually do a lot) that would mean a lot of socket connections. And I'm not sure how long it takes for a websocket to establish connection.
So there a 4 ways to do this:
HTML via AJAX - probably the most stable way that doesn't need a lot javascript to do the templating - Browser can use open HTTP connections to request stuff.
HTML via socket.io - The websocket must be established to load content (may be slower)
API via AJAX - as it probably needs more requests as HTML via AJAX there might be some HTTP header overhead + you need to authentication in each request- I'm not a friend of too many ajax requests.
API via socket.io - Socket must only be authenticated only once and you can request API objects on the fly. However I would still load templates and js via HTTP for browser caching.
I know this is a huge post but I'm debating for many days now and just can't decide as it would be a lot of work to switch the system once started developing. This is not a public project, it's limited to ~10k-15k local people and thus must not be that perfect, a good opportunity to learn new things in my opinion (I'm completely new to node, classic PHP MVC + jquery dev here).
I think you should use a RESTful api on the backend, let the templating occur just on the frontend (maybe with Backbone) and only use Socket.IO for real realtime stuff (such as chat). It doesn't make any sense to use websockets for something like loading HTML, because it most likely never changes.
So my vote is:
1) HTML via AJAX
2) API via AJAX
3) Realtime communication, such as chat messaging (or other stuff that constantly changes) via Socket.IO
Though there really isn't a definitive answer, as it depends.
If you need to be search engine crawlable, you can NOT rely only on client-side processing. If your individual views are light, and/or you need to support mobile, you should have initial rendering server-side.
Currently, I would suggest using an API that both your client application and server-side can use. If you use node for the server-side rendering you can re-use a lot of the same logic, including the API client.
Going a few steps farther, if you look starting with the Yahoo flux examples project on github, you can use the same logic both client and server-side including rendering with React views. This is not an easy solution, and will take some work.
For interactive elements, server-side rendering can be minimal with your stores pushing an event wiring up via sockjs/socket.io when the client starts for your chat/im bits.
You will have scalability issues when it comes to running across multiple processes and will likely need a pub/sub chain backed by a db for longer re-connect cycles or missed IM messages. There isn't a magic bullet.
Right now, I like flux+react... When Angular2 comes out, it may have a better story for server-side rendering.