Can you create an express api for an existing domain? - node.js

Let's say I have a domain already running called http://docs.domain.com.
This isn't an express server it's something I don't have control over, however I do have full control over the source files, so I was hoping there's I way with ExpressJs that I can sort of reverse proxy a restful app?
So http://docs.domain.com/app/products and that would get data locally?
Or is there something else I can do with node to save a file locally from the website?

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Why does backend development need a seperate server?

I am developing my own website. So far, I've used React for the frontend and Flask for the backend. I've been doing frontend development for a while now but I'm just starting to get into the backend.
From my limited understanding, frameworks like Flask and ExpressJS create their own servers and host data that the frontend can use. It seems to me that that they automatically create websites to host and receive data. In my website, I route the backend to do what I want and use fetch requests with POST and GET from the frontend to communicate.
Although it works, to me, it seems overly complex. Why does the backend need it's own server? It seems unnecessary to create a proxy for the frontend and fetch data. Why can a website not just run custom code in the background, why does it need a service like Flask or ExpressJS to run in the background for it? These backend frameworks run Python or NodeJS in the background, but wouldn't it be much simpler if the website itself could run Python or NodeJS in the background?
I also see that in frameworks like React, you can import things and use modules— like in NodeJS. While importing some modules works, the require keyword is not allowed and normal NodeJS code will not work. Therefore, the backend will not work. Why is this— why can't you just run backend code natively? Instead you have to go through fetch and specify headers to basically translate information from your frontend to your backend.
Forgive my amateur understanding of web development, but the frontend/backend system seems overly complex to me. Thanks in advance.
Why does the backend need it's own server?
Where will the client store data so that when you open the page again the data will still be there? You can use localStorage but this is locked to that particular browser. What if someone logs in on a different device or uses a different browser?
Where will the client get the application from in the first place? Your application needs to be packaged up in a form that can be easily downloaded, and it needs an address to be loaded from. This is all considered "back end" even if you're using a static hosting service like GitHub Pages.
There's a lot of reasons why a back-end exists and needs its own server. Any application with persistent state which is expected to work across different sessions needs at least one of these.

How can I use react with a custom webserver?

I want to use React for a project I am working on, but I also want to use an API.
How can I do it?
I have tried to Google this and ask different people, but I have not got a response yet, so I thought I would ask here. I want to use express and maybe not use create-react-app (as it takes up a lot of storage).
Working on a custom server doesen't preclude the use of an API.
If you want fetch the API from the express server and inject it directly on react frontend you need to enable server side rendering (useful post) and pass the data collected as a props from the server (check this example).
Rather then you can build your react project (using even create-react-app) and build an express server who return the index.html on call.
Personally I prefer the first one solution.

Vuejs frontend served by Express and backend API in node security practice

I am currently working on a small project where I used vue.js to build the front end and express.js for the backend.
For the frontend, I have another express server to just serve the static files and all the requests will be redirected to my backend API with proxy by the frontend server.
For the backend, it is just an Express API app.
Both apps are runing on heroku right now. And my questions is:
What is the best practice to connect the front end and back end server, I did a lot of research online and people are saying backend API are not supposed to be exposed to internet? I am not sure how I can talk to my backend if it is not on internet.
For the frontend, I can use SSL/TLS to protect the connection. But for frontend to backend server communication, what should I do to protect this data transfer, can I use another SSL/TLS? And should I use some mechanism to verify that the request is sent from my frontend server, not somewhere else? If so, what is the recommanded way to do that?
A lot people say that there should not be direct connection with database, it should go through a web service for security. What does that means? Now in my backend Express app, I have line of mongoose.connect('mongodb://someaddress/myapp'); Is this bad practice? If so, what should I do to make it more secure?
Please try to be more specific, I am still new to theses and try to learn, code examples can really help. Much appreciated!!
Vue and Express apps are written in the same language, so it is best practice to have these as separate projects as you have done. These are entirely different projects doing different things so they should be split.
You already deployed to Heroku, so the SSL/TLS isn't really a concern for you. However if you were deploying to your own VPS, you'd want something like Let's Encrypt. For restricting requests from Express to your Vue app, you'll want to look into CORS. See expressjs/cors for more details.
The Express app is the service connecting to your database. If you were trying to directly connect to your database from your Vue app, then that becomes an issue. You would coupling client side code with server side code. What you're doing is fine.

How to integrate a Nodejs API with ReactJs app under the same domain

I'm trying to understand how a MERN app fully works, I've been reading about MongoDB, ExpressJs, ReactJs and NodeJs, I also understand how MongoDB, ExpressJs and NodeJs interact and how ReactJs works on its own, my question is simple (I think).
The question:
If I create an API, using Node,Express and Mongo, and I have an APP managed by React, both need a server (via express, I understand), then, how should I run the API and the React app at the same time. Do I need different URLs? should I configure different ports? how should I integrate them?
I really been reading a lot, but almost every tutorial is made locally (and I'm working in a server with Passenger and I can't change the way it starts), just for Node/Express(with pug or else)/Mongo or just React, and I don't understand how to connect the API and React.
Thanks
It depends on several factors: environment (e.g. development, production), and your control over the server. For development, you can have two different URLs and use something like Webpack Dev Server. Normally you would have the module bundler, e.g. Webpack, watching for changes in your React code. However, this can get more complex if you have Server Side Rendering.
For production, normally you would have the bundled file for your client side application already optimized and minified. If you can change your API, you could serve it statically in a new endpoint, for example: /static/bundle.js and request this endpoint from your index.html file, which will be sent by Express.js server when accessing /.
However, because you will probably want to have routes in your React app, your server will need to know how to handle the client app routes (for example app.get('/*', () => ...), and they could collide with your API endpoints. To solve this, you could:
Prefix your API endpoints with a namespace, e.g. /api/v1/...
Place the API in a different URL, port or subdomain. In this case you would indeed need to run these two servers in parallel. With Node.js, there are helpers to make this more convenient, e.g. concurrently.
Pulling out your concerns: API, React, and Integration for MERN app.
I use three approaches
1) Use foreman. With this, you can specify your API and Web Client in the Procfile. I used it here
2) Use a proxy to handle requests that require your API. So in package.json, you specify your API URL(your API must be running)
// package.json
.......
.......
"proxy": "<path to url:[port no if you're developing locally]>"
Check here.
And you can simply add a script to run your API and React concurrently.
3) Set your API and React app in a Docker container. mern-starter is a perfect place to check for this.
Hope this helps!

AngularJs: How to upload images to another service?

I am building a MEAN application (Angular + node + Express + Mongo).
In this app there are users who can upload a limited amount of pictures (lets say 5).
I really want to avoird storing too many data on my server.
So I am looking for a module that let users upload the images to a service such as picasa, imageshack... The service should be transparent to the user.
When it's done, I save the picture URL in my DB and so I can retrieve it and display pictures easily.
Do you know such module / tutorial to do that? Does it even exists?
I have been looking but it seems to not exists.
The easiest way to have a file upload service with AngularJS as the front end and NodeJS as the backend is to use the jQuery File Upload for use with AngularJS, which can be found here.
It makes use of a directive that you can use to upload your file.
You need to specify a route to which the uploaded file should be POST'ed to.
In this route handle, that is in you Node.js server, you can then post it to the external image hosting servers. This is something that you can write on your own or you can use the node.js modules for the respective hosts (if they exist).
I find a service doing it:
http://cloudinary.com/
With a nodejs integration:
http://cloudinary.com/documentation/node_integration
It seems perfect (free up to 500 MO and 50.000 pictures, far enough for my needs).

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