I am building an iOS app with react-native and looking to do some web scraping. From my understanding traditional npm packages don't work because they rely on Node.js. I know there are Objective-C/Swift libraries for web scraping but I don't understand how I would integrate those into a react-native component.
Anyone have any ideas on how to get information from a website (web scraping) in react-native?
Interesting question. Architecturally, it might be a good idea to consider building a service which can provide the scraped data via an API. The more processing power the client requires (the heavier the client-side code), the more likely you are to run into lagging / stuttering issues in the app. Phones have come a long way, but still can't match a server's power.
If you want to press ahead, I would advise using the browserified version of Cheerio.js. Basically, browserify lets you take code written for node, and use it in a browser environment. You would need to test it in JS Core on IOS, but there's a good chance everything will work.
One other option is using jQuery's load function or the fetch api included in React Native to make the call to the site (you don't have to worry about CORS), and parse the result manually.
Related
I plan on making a desktop only app. I don't have any intent to deploy it to a web server. Think something like VS code.
Im used to just "throwing" react at any problem that has the term "web application" in it. It streamlines so much its almost impossible to write really great apps without it in my opinion.
However, electron is a different beast entirely. Should I use react still, or is there more benefit to just sticking with raw electron in my case? I'm fairly new to development in electron, so I would like to do it right.
Electron is actually Chromium browser on the front end and nodejs on the backend. Building an electron app is technically building a webpage which ships its back end along with it.
If you have a dynamic application that needs to rerender frequently, ReactJS’s virtual DOM will be super effective
So, if you're used to 'throwing' react at any problem that has the term 'web application' in it, i would suggest you go with reactjs.
Use case
I've got an existing project developed in C# using WinForms with custom controls for the GUI. We are amazed by the approach to write GUIs using HTML/CSS/JS and we are looking for the best way to write a GUI for our desktop application using the above mentioned languages. We only need to support Windows devices.
My worries:
It doesn't take long to come across recommendations using electron-edge. While I am not so worried to get everything working, I am worried about:
Debugging my C# code (I still want to be able to start my whole application right from VS and debug it look I am used to it). I read that I would need to attach to the node.js application in order to debug my C# code afterwards. Since the whole program language is written in C# that sounds like a pain?
As far as I got edge will let it run as just one process. Can I consider the electron application as an own thread which would still run while my C# code is stuck somewhere?
My option:
I am still positive I want to write my desktop GUI with HTML/CSS/JS. What I considered instead of using electron-edge is writing an own electron application which does communicate with my C# backend using named pipes. I wonder if there are larger roadblocks why I wouldn't want to do this and use electron-edge instead?
My question:
I would like to get feedback for my two concerns mentioned above and I also would like to get input about my option to create the GUI as own electron process, so that I have two processes (GUI+Backend) when someone runs my application.
Electron.NET may be a option for you. You can write c# code with electron.
You can do it in many ways
1) COM. Create C# COM DLL. Create wrapper functions for the DLL using N-API (Native node module) or use FFI. You can access the functions from JS.
2) Create a .Net web server and include your functions as REST endpoints. From UI make http request to communicate (Clear separation of UI & BEnd)
You can checkout my github repo for a few alternatives to electron.
I think a most import question would be how your frontend interacts with the backend? Is there any notifications need push to the frontend?
WebSocket could be a good option for two ends communication.
I want to develop an android application which is to integrate a visualization from d3.js. Is it possible? Can anyone explain how to do this.
D3 is a library geared towards manipulating data and rendering it into an html DOM –– either via SVG, or straight up divs or perhaps a canvas. Of course there also needs to be a JavaScript engine that can run the code. Browsers provide all those things; native apps provide none of them out of the box.
However, there are ways to build native apps that wrap a javascript engine and DOM. PhoneGap is a commonly used framework for doing so. It essentially lets you develop as if things are going to run in a browser, but they're packaged into a native app. There's a performance hit to that: It won't run as fast as a native app, and often not even as fast as the same code would run in a mobile browser. But from the user's perspective, it's installed and launched just like any native app.
That's AFAIK the only way to use d3 in a native app.
I have a small python program to help my colleagues to analyse some tsv data. The data is not big, usually below 20MB. I developed the GUI with PyQT. I want to change this desktop program to a web app so my colleagues don't have to upgrade the program every time I change it or fix a bug. They can just go to a website and use Chrome as the GUI.
So how do I do this? I spend most of my time developing desktop program and just know some basic web developing knowledges. I have read some framework such as flask and web2py, and know how to use HTML and Javascript to make buttons but no clue to achieve my purpose.
Can someone give me a practical way to do this?
It'd be better if the user don't have to upload the local data to the server. Maybe just download the python code from server then execute in Chrome. Is this possible?
Thanks.
No, you cannot run Python code in a web browser.[1] You'd have to port the core of your application to JavaScript to do it all locally.
Just do the upload. 20MB isn't all that much data, and if it's stored on the server then they can all look at each others' results, too.
[1] There are some tools that try to transpile Python to JavaScript: pyjs compiles directly, and Emscripten is an entire LLVM interpreter in JS that can run CPython itself. I wouldn't really recommend relying on these.
The whole point of a web application is that the GUI is written in HTML, CSS, and JavaScript, not Python. However, it talks to a web service, which can be written in Python.
For a well-written desktop app, the transition should be pretty easy. If you've already got a clean separation between the GUI part and the engine part of your code, the engine part will only need minor changes (and maybe stick it behind, e.g., a WSGI server). You will have to rewrite the GUI part for the web, but in a complex app, that should be the easy part.
However, many desktop GUI apps don't have such a clean separation. For example, if you have button handlers that directly do stuff to your model, there's really no way to make that work without duplicating the model on both sides (the Python web service and the JS client app) and synchronizing the two, which is a lot of work and leads to a bad experience. In that case, you have to decide between rewriting most of your app from scratch, or refactoring it to the point where you can web-service-ify it.
If you do choose to go the refactoring route, I'd consider adding a second local interface (maybe using the cmd module to build a CLI, or tkinter for an alternate GUI), because that's much easier to do. Once the same backend code can support your PyQt GUI and your cmd GUI, adding a web interface is much easier.
If I get your point correctly, you want
Web connection, so your python program updated on server, client get it before using it.
Data store on local to avoid upload big file.
You can write a python program to check a server location to get your latest program if needed. You need a url / server file for program version / created date/time information to determine if you need to update or not.
After get latest python program, then start this python program to run locally.
With this said, What you need is to update your program to add below features:
Access your server, to get latest version information
Check against current version to see if you need to download latest program
Download latest version and use that to run locally.
Does this solve your problem?
Trying to understand using node.js for a web applications.
Are there basically 2 major uses cases, i.e.:
The entire system is written in node, so you have functions for login, logout, password recover, and whatever else the web app does. All of this is written in javascript?
You use node.js only for sending the client updates, to have a real-time effect on the app. But the rest of the application is written in e.g. rails or django
Please tell me if I understand this correctly:
In terms of other technologies used with node.js, you tend to see people using node.js as the backend server, socket.io on the client side to establish a cross-browser long running ajax call library, and then you might use backbone.js for your client mvc pattern.
Is this right?
Basically speaking, it is just a tool to run javascript code server side. What you do with it is up to you. Many are using it as a complementary system since it's relatively new, but it's perfectly possible to run an standalone app with node.js.
It's said to be particularly good at handling concurrent connections, which is why it is often recommended to handle real-time jobs within an app, but there is no "obligation" so to speak to use it for this specific use case, it's just one thing you can do.
As with everything, the best way to understand it is to use it, so don't be afraid to play around with it.
Use case for Node js as we are using in our Application
Skype like voice & video chat on chrome browser using node js