I have an unusual web application similar in some ways to the live versions of DriveWorks and KBmax. The Logic, Interface, and Tables are created in a windows application by sales teams and engineers throughout the company and stored in sql server. In the Web application, when a user clicks an item in the product menu the the Logic and Interface are pulled from the database, compiled using CodeDOM into an InMemory executable and stored in Session variable. The Front interface in web application is dynamic and invokes the executable in session for the control logic events. The Tables are also stored in a DataSet in Session. At any rate, this all actually works, but seems to have random quirks that are hard to pinpoint. I'm wondering if this is way to much to put in session and alternatives.
Note: I am using javascripting where I can, however since the code is actually created by other users there is also a lot of postbacks going on. When I run this using my localhost it seems to run acceptable, but on the host server it seems clunky.
I have this same application as a Windows application and it works great, just trying to make the web version.
If 64bit process is used, using session should not be a problem. If 32 bit process is used you should look at out-proc (db / windows server AppFabric). Regarding random quirks, i guess something to do with code.
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I have created an application using javascript library D3. Users will constantly click and drag to frequently change graphical elements and I currently save the data in 3-4 local javascript objects and arrays. I want to save the data to the server periodically rather than after each change. Also I want them to be able to work if they are not connected. From twenty years ago, I imagine doing this manually where on the client side records are flagged as “new”, “revised”, and “deleted”. Every 10 seconds client data is saved via AJAX and either an object is updated or a SQL statement is executed. An id is returned from the database and saved on the client side to track each record for future modifications.
Note the data must be organized in a database for ease of separating elements for reuse. When the user is connected, updates every 5-10 seconds are fine. Then I can use an inexpensive and slow server. Of course a tool that deals with records that might not fully update is good, perhaps some transactional functionality.
There will be no separate mobile application. I can modify my javascript objects to be json compliant if need be. I see there are “offline-first” frameworks and javascript "state containers". Redux caught my eye, especially when I saw its use climbing over the years according to Google Trends. I’ve read about so many options and am thoroughly confused by all these. Here is a mish mash of tools I looked at: Store.js, now.js, indexedDB, couchDB, pouchDB, Cloudant, localForage, WebSQL, Polymer App Toolbox, Hoodie framework, Ionic and angular, and Loopback. Not to mention XHR, web sockets.
I have used MVC like Laravel and Zend, both are with PHP and MySql. I wonder if I could integrate the suggested solution. Thanks.
Related: How do I sync data with remote database in case of offline-first applications?
Saving the data locally using PouchDb and then syncing it with a CouchDb database (or IBM's Cloudant service) when a network connection is available is a well-trodden path for this sort of requirement. But your question is asking for an opinion, so there will be many other perfectly valid solutions to this.
I'm still new to web development. To learn more about JavaScript(JS) and web development, I am thinking of writing a simple web app which pulls and records time-series data (say, the price of a stock) periodically and draws a live chart showing the historical data. In addition to price data, I would like the app to record/maintain some user-related info such as the ticker of the stock(s) associated to each user.
Ideally, I would like to keep the app light-weight and portable/standalone (meaning, reduce the dependency as much as possible, and the end user hopefully doesn't have to do a lot of configuration/install of dependencies). The issue that I cannot figure out is where to store the historical data. I looked around for database solutions which will allow the app to write data directly from the browser (that is, using JS) to the client's machine. LocalStorage and IndexDB are non-persistent as far as I understand. Some suggested using PouchDB, but upon looking at it closer, it seems like the user need to install CouchDB or some compatible DB (say, SQLite). But that means I cannot share my app with users who aren't technical enough to install and configure CouchDB or SQLite on their machine before using my app.
If anyone could share some insights as to which DB might allow a JS-based app to write persistent data to the client's machine (if such thing even exist), that would be greatly helpful. If there is no such DB solution, please feel free to let me know alternative solutions that would allow the goal of building a simple, portable, JS-based web app. Thank you!
I think the best solution is to use Electron.js. The whole idea of this framework is to create web apps that can reside on client machines. You could package up any DB option you want, or even better, just include an API to your backend through the web app and it will work on your client machine like I think you want it to.
As for DB options, there is a great thread on S.O. that talks about what is possible. It looks like knex.js is your best bet (full disclosure - I haven't used knex).
I have a simple offline html5/javascript single-html-file web application that I store in my dropbox. It's a sort of time tracking tool I wrote, and it saves the application data to local storage. Since its for my own use, I like the convenience of an offline app.
But I have several computers, and I've been trying to come up with any sort of hacky way to synchronize this app's data (which is currently using local storage) between my various machines.
It seems that chrome allows synchronization of data, but only for chrome extensions. I also thought I could perhaps have the web page automatically save/load its data from a file in a dropbox folder, but there doesn't appear to be a way to automatically sync with a specific file without user prompting.
I suppose the "obvious" solution is to put the page on a server and store the data in a database. But suppose I don't want a solution which requires me to maintain apps on a server - is there another way, however hacky, to cobble together synchronization?
I even looked for a while to see if there was a vendor offering a web database service - where I could, say, post/get a blob of json on demand, and then somehow have my offline app sync with this service, but the same-origin policy seems to invalidate that plan (and besides I couldn't find such a service).
Is there a tricky/sneaky solution to this problem using chrome, or google drive, or dropbox, or some other tool I'm not aware of? Or am I stuck setting up my own server?
I have been working on a Project that basically gives you versioned localStorage with support for conflict resolution if the same resource ends up being edited by two different clients. At this point there are no drivers for server or client (they are async in-memory at the moment for testing purposes) but there is a lot of code and abstraction to make writing your own drivers really easy... I was even thinking of doing a dropbox/google docs driver myself, except I want DynamoDB/MongoDB and Lawnchair done first.
The code is not dependent on jQuery or any other libraries and there's a pretty full features (though ugly) demo for it as are well.
Anyway the URL is https://github.com/forbesmyester/SyncIt
Apparently, I have exactly the same issue and invetigated it thoroghly. The best choice would be remoteStorage, if you could manage to make it work. It allows to use 3rd party server for data storage or run your own instance.
I have to design an webapp that has the capability of working offline.
So there are many working points that in normal mode work online , connected to a central server.
Now there are moments when for different reasons , the central server might not be available.
(no internet ,server crash etc) so then is needed to enter in offline work mode.
Is not required to work fully just to do some work because clients should not wait , so invoicing should be possible (concrete case).
A custom solution I already have in mind but I am wondering if you know a framework or something that does such things already.
Thank you !
We wrote a desktop app for hundreds of employees to use on their laptops. It used database replication to merge the data from the laptop copy of the database to the server copy of the database. The amount of data contained in the database was significant -- product information, customer contact information, and so on. That was all needed for the rep to be able to create sales orders and invoices and the like. It was crucial that the rep be able to use the software all the time, not just once in a while when they had connectivity. However, this approach does have its challenges -- if the local databases don't get synched up frequently, data at both ends becomes stale, plus you have to deal with conflicing updates.
If the amount of database information needed locally for working disconnected isn't huge, you definitely can take advantage of the new HTML5 offline storage and use a website.
I think that the critical factors here are how much data the user needs when they are working offline, how fresh the data needs to be, and what percentage of time they will be working online vs. offline.
If your app is html/javascript, use the HTML5 application manifest. See the following resources
http://www.w3.org/TR/offline-webapps/
http://www.webreference.com/authoring/languages/html/HTML5-Application-Caching/
You can use Google Gears.
Here is another link: http://www.scriptol.com/ajax/google-gears.php
I've written a simple web page that uses Javascript to control a Quicktime plugin for movie playback. There's also some AJAX stuff using jquery to get info on the movies from an MSSQL database. The web page is served to the user from an Apache 2.0 server, this also hosts MSSQL. The end users will view the page in IE6 (unfortunately).
My problem is that the end users now want to use an RS422 jog/shuttle deck control to drive the movie timeline, in place of another jog/shuttle unit that relied on emulating keypresses which was easy for me to detect.
As I'm not a programmer I'm at a loss what to start looking at for a solution to receive the RS422 data and then send that to the Javascript to control the timeline. Is this something that a custom activeX bit of code could do? I've googled ActiveX with Javascript but it's unclear to me (as a novice) how the two work together, or whether this would be suitable at all.
If anyone could give me an overview of what to start researching that'd be much appreciated.
Many thanks.
Jon
JavaScript runs in a sandbox and has no access to the computer at all (for security reasons; you really don't want to make it any more simple for frauds to get at your credit card data).
ActiveX would work but it's a security risk, too. ActiveX is written in C++, no JavaScript there. You'll find information about that on the M$ Website. Note that ActiveX is usually disabled today because of said security risks. Depending how serious your client take security, the virus scanner might not allow to start an A/X control.
Another option would be to write small program which is installed on the client's computer that reads the serial port and send that to the web server where your JavaScript can query it. Okay, that's more than a bit convoluted but probably the least risky.
Or you write a program which transforms the serial codes into key presses (just create the event and post it to Windows). Again, you need C++ or maybe Python with the win32 package.
Your client must understand that this is something which sounds incredibly simple but you'll have to jump through a lot of hoops to make it work. A web browser is not a local application with full reign of the hardware (and it must never be).