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Julia as Server side

I need to make a web page where the input and the output is displayed, but the code where I "do stuff" must be in writing in Julia, how can I do this?.
to be clear, I want something like this:
Web ----> Julia ----> Web
|input | do stuff | output
I don't know what I need to make this possible, I need any kind of Server-side?
I'm a very novice in programming, so I don't know how to search this on internet, I will be thankful with any help.

In addition to the Julia webstack, you might want to look into Genie.jl. It's looking like a nice framework and was used to build this website.

If you need to accept input from the web and then output corresponding data after processing it with Julia, then definitely you need to use some form of server side Julia, since Julia does not run in the browser.
In terms of workflow, what you need is very simple:
1/ first, you need to display a form, to accept user input;
2/ second, the form needs to be POST-ed back to the server - where the data in the payload is processed;
3/ finally, you need to send back a response.
You can use a Julia framework like Genie (author of Genie writing this, btw) to have everything Julia in your stack - or you can use some other web stack (PHP, ruby, python, etc) for 1/ and 3/ and have a local Julia script process the data, invoked by the web scripts.
If you don't have experience developing web apps but have/need Julia skills, you're probably better off using Genie. It knows how to render HTML, it provides a nice MVC workflow, has a clear file structure and comes with some generators, does input sanitization in the persistence layer, etc. And it's very easy to accept input, add your data processing logic, and output your response.
But I must warn you that it's still very much work in progress - and this is visible in the state of the documentation (working on it, but boy this is time consuming). You can give it a try and open up issues in GitHub if you get stuck. Also, I would not recommend it for any mission critical apps yet - it needs more testing.

I will copy part of the answer from: How to make a GUI in Julia?, and add a few more.
If you are developing you code within an [Jupyter/IJulia] notebook,
and need very simple interaction, such as slider to change some input
values, the Interact package is the easiest thing to get started
with.
To develop full fledged web UIs, take a look at Escher.
Inspired by the Elm, it provides a functional library of UI
components. Interactive web UIs are created in 100% Julia. There is
no differentiation in code between the client and server sides. The
framework handles all of that.
Another web framework worth looking at
is Genie, which based on the traditional MVC design pattern. It also
includes an ORM. An example of an application written in Genie is
this listing of Julia packages: http://genieframework.com/packages
If you application is relatively simple, and you are happy working with a slightly lower level API, the Mux.jl middleware framework (which Escher uses) allow you to write simple handlers to http requests.
If you want to create cross platform desktop apps, but want to work with
web technologies (i.e. HTML/CSS/Javascript), use Blink. This is a
Julia wrapper around the Electron. You could potentially write an
Escher or Genie application, and wrap in in Blink.jl to create a desktop app.
All of these packages are currently useful and well maintained. Unfortunately, some of the higher level frameworks in juliawebstack are no longer maintained.

Implementing a RESTful API based Web App. Do I need a server-side framework?

I'm starting a project that basically is a single-page app that downloads and shows a bunch of stats (using d3.js). The data layer is Mongo-powered, served through a RESTful API, and the client app will be coded in Ember.js. We want all data to be exchanged through the API, since we also have some mobile apps in the back burner that will hook to the same API.
I'm debating on whether write the API (using Express.js or other server-side MVC framework), or just serve the API use Deployd and not using a server-side framework at all, besides Deployd. I'll provide some hints about the project characteristics:
The main feature is basically a dashboard that shows aggregated stats that are already computed and stored in the Mongo database.
User interaction is minimal, enough only to allow users to customize their dashboards, but users never upload data (other that customization preferences).
Most of the app is a lot of d3.js to create and render a bunch of graphs, which can customized in many ways.
It requires a very rich and responsive user interface.
I proposed skipping completely the server-side framework, and simply go with a bunch of static HTML+CSS and do all the heavy lifting with a client-side MVC such as Ember.js. Since all data download and upload can be handled by Deployd, a pure static site would load much faster and is also easier to scale. Also, (I think) all user-related data and validation can be done with Deployd itself.
The thing is, some of my colleagues had a heart-stroke when I mentioned this idea. So I'd like a reality check: do I really need a server-side framework besides Deployd to cope with problems I cannot foresee yet? Are the benefits of having a pure static site a good enough tradeoff versus having, say, Express.js just in case?

I haven't worked with Deployd before, but from a quick skim of its docs, it is a server-side framework. It accepts requests and respond with json. It's just oriented to APIs and json and neglects html, unlike, say, default Ruby on Rails.
The main issues I can think of that might arise due to a lack of a traditional server-side framework are things like auth, CORS, and XSS/CSRF/other common security issues. You could cater for this through Deployd if it's built in or easily added, but that may be difficult.
Looking further into Deployd's docs, I see there's a guide for users and CORS. I can't find anything about XSS or CSRF.

Writing Real-Time apps with NodeJS

im looking forward to build RT web apps with NodeJS. Coming from Rails, I've felt in love with NodeJS and Async JS programming.
Run a few experiments with Node, and then as I search tools and resources to get used with, I got overwhelmed with the lot of stuff over there.
I found lot's of libraries and components over there, and pretty much got confused on how a large-scale well-writen and implemented RT web app should be built.
So the app will run over NodeJS, using Express framework.
I read about knockout.js, a client-side library to provide realtime stuff like automatic UI refresh, and I guess I could conbine it with jQuery.
Also, I found socket.io.
The author says:
Socket.IO aims to make realtime apps possible in every browser and mobile device, blurring the differences between the different transport mechanisms. It's care-free realtime 100% in JavaScript.
So socket.io is about compatibility.
What about backbone.js? Where does it goes to?
With so much stuff, I got shocked. What should I learn? Which modules worth studing?
Im focusing on NodeJS and Express but most books/screencasts covers old versions of nodejs. So im being guided by its official API.
Now im here asking your advice and to organize somehow all the info out there.
Correct me if my assumptions are not precise, please point me to the right direction and feel free to suggest any other module that could help on my learning.
Thanks in advance

It might be useful for you to separate the node.js server side libraries (via npm etc...) from all of the client side (browser) libraries and technologies like jquery, backbone, knockout etc... when you think about it. Even socket.io which exposes a persistent socket connection between the browser and the server (to avoid polling) does not dictate what client side technologies you use.
Focus on exposing a solid web-api ( random example ) from your server and your client technologies can be swapped, augmented etc... with no effect on the server. The only place they intersect is if you're using a view technology like Jade. It's also an option to have a pure separation where the server is just serving up the client files and your client is a thicker javascript application (using knockout, jquery etc...) calling a good server web api.
Some folks try to unify the client and server models - for example, this article using backbone and node. It depends on how much data you work with to say whether that's feasible but it does couple the client and server and makes the server stateful which can have downsides (scale out, requires affinity etc...). Personally, I get wary of that much magic (binding, state, syncing etc...). Node is about keeping things simple, light and fast. It's a fast front end network server.
My 2 cents (and some may disagree). Start with node on the server and pick your storage (mongoDb etc...). Design a solid RESTful (hypermedia) API - a good webapi regardless of the client. Then start with a basic html/css/js, maybe jquery client and add things like knockout etc... as you expand your client skills. That will allow you to replace your client technologies independent of your server as the new technology winds change (and they will).
That's the hallmark of a well designed system - the ability to replace componets/sub-systems without rewriting everything :)
Hope that helps clear up some of the fog :)

You may want to look at Meteor if you are focussing on real-time Javascript apps: http://meteor.com/

Is Node.js a good alternative to build complete websites?

I'm wondering if using Node.js (express.js) is the best option to go for a complete website. I've been using Rails + Node.js and am wondering if this is still the best option or if I should move completely to Node.js.
Are there websites built completely with node.js? I imagine it must lack many things Rails offers.

I imagine it must lack many things
Rails offers.
I gave a short list below but I would like to know what you could be missing and I think(almost certain) we can give you some alternatives on node.js.
Modules
node.js is getting pretty complete and I think you can run your entire site using only node.js using for example the following modules. I assume you know about npm. If not I really advice you to google for it and learn that. To search npm you can use http://search.npmjs.org:
web framework:
High performance, high class web
development for Node.js
https://github.com/visionmedia/express
Socket.IO aims to make realtime apps possible in every browser and mobile
device, blurring the differences
between the different transport
mechanisms.
https://github.com/learnboost/socket.io-node
I believe with these two web-frameworks you can create a lot of sites. For example express is a very powerfull web framework and supports a lot of cool things like:
session support.
a lot powerful template engines. I like Jade for example. You could also share these between client and server a lot of the times easily.
excellent routing.
just to name a few.
database:
Redis is an open source, advanced
key-value store. It is often referred
to as a data structure server since
keys can contain strings, hashes,
lists, sets and sorted sets.
https://github.com/mranney/node_redis
MongoDB (from "humongous") is a scalable, high-performance, open source,
document-oriented database.
Mongoose is a MongoDB object modeling tool designed to work in an
asychronous environment.
https://github.com/learnboost/mongoose/
With those two databases I think you should be able to accomplish most of your tasks. The nice thing is that Redis is extremely fast/simple advanced KV-store(dataset in memory/also supports VM) and supports replication while Mongodb is more completely(slower then redis) and also supports sharding.
authentication:
Authentication and authorization (password, facebook, & more) for your node.js Connect and Express apps.
https://github.com/bnoguchi/everyauth
Like I said previously you can get a long way with only these modules.

Express.js is more akin to Sinatra. They're simpler frameworks than rails.
Express's list of sites is fairly small http://expressjs.com/applications.html
So I think it's also good to look at Sinatra's list http://www.sinatrarb.com/wild.html
So to answer your questions in reverse order. Yes it lacks all the features of rails. Yes there are sites written completely in Express. And going to 100% Node.js might be the right decision for your site.
It depends on which features you'd miss and what performance you need.

I'm not sure, but I guess it's perfectly possible. I have built complete sites using plain server side javascript for years without problems. The advantage of node.js seems to be its event driven model and things like socket.io. I just started experimenting with it, I'll probably will try porting an existing site to node.js.
Here you can find a large list of sites built with node.js.
Finally, you may want to read: What it’s like building a real website in Node.js

Yes, as of now node.js lacks many (well, at least a few) things rails offers. Eventually the set of available node.js modules will collectively provide good alternatives to RoR across the board. Or at least different (and often more modern) approaches to the same fundamental problems. There are still some important things missing in the node.js ecosystem including a good ORM for postgresql (rails has ActiveRecord which is great) and a good DB schema management subsystem. Both of these do not exist in the node.js ecosystem as of this moment, but surely they will be there in due time. Rails has these down pat right now.
There are some tricks node.js has that RoR doesn't. Debugging in node.js is more seamless than RoR and express.js is more flexible. Express is the library approach (you tell it what to do) whereas rails is the framework approach (you fill out the boilerplate it creates for you). There are also some fantastic things like stylus and jade, which have equivalents in rails, but when you have a full app written in one language (either javascript or CoffeeScript, which I prefer) and everything is in a modern node.js/TJ Holowaychuck style, you get a level of cohesiveness that is really nice to work within.
The other thing to keep in mind is that while the list of available node.js modules is quite impressive, many of them are not as mature and battle-tested as their rails/django analogs. It's hit or miss, so beware.

Pure JavaScript-based clients

I would like to know, how powerful/viable are JavaScript only clients based on say, GWT/gxt/vaadin, when compared to DHTML clients such as those made with wicket, tapestry, click etc?
My boss has insisted on using GXT (due to its nice colors and theme) on a project that will most likely become very big with lots of screens. I am against the idea of a javascript only client, especially when the javascript is generated from Java code. I have tried to advice him that we use something like wicket whereby we construct the screens with html but put in ajax where and when neccessary.
How viable is such a JavaScript client? I understand that JavaScript was intended for minor web page enhancements, and not all browsers, especially mobile devices have complete support for JavaScript.

Yes, it is viable for certain applications. Consider Gmail, Google Docs and Google Maps as typical applications where this works, and is probably the most feasible approach.
Some rich UI JavaScript frameworks, such as Ext JS also rely on this technique.

I've built javascript only web apps for ages.
First in SAP projects for big multinationals. And now on a new project:https://beebole-apps.com?demo
So yes it is powerful and viable.

Javascript-only webapp can be extremely powerful, and it's viable for certain applications, say, an Instant-Messenger webapp?
You mentioned that there are lots of screens in your web-app. One of the advantages from GWT/GXT is the fact that you can unit test your UI-layer with JUnit. This is an extra testing you can do on top of, say, Selenium. This is essential if you'd like to make UI testing a part of the continuous integration process, and, as the team grows, you'll definitely want to have tests around to make sure everything works (At least in theory.)
However, if what your boss meant to do is to build an in-house, custom Javascript engine using GWT's JavaScript Native Interface (Link), then I'm not sure...
Another advantage with GWT-like-engine over Wicket is that you can rely on HTML-code-gen to generate standard-compliant (In theory) HTML code. With framework like Wicket, it is hard to ensure every single developer on the team to author good HTML code - Especially when the team gets bigger.

Disclaimer: I'm a member of the Vaadin team.
Our Timeline demo is a good example of what can be achieved with Vaadin and GWT in client side, but I think all of the options presented in this discussions are viable given enough time.
Since you are going to start a big project you should build a simple proof-of-concept app with each of the relevant frameworks. If your PoC includes at least some of the more complex use cases you'll probably can make a pretty informed choice based on the experiences you get while building them.
I urge you to at least evaluate Vaadin. With it you write only server-side Java code and Vaadin will create a slick and professional browser UI for you. Client side can be easily extended using standard GWT (also pure Java), and there are no HTML templates, tag libraries or XML configuration involved at all. A Vaadin UI is fully Ajax'ed and lazy loading out of the box, and it easily integrates with any server side technologies, eg. Spring.
In addition to the development model advantages you get top-notch documentation, a bi-weekly update schedule, a very lively community filled with helpful experts, 100+ useful open source add-ons, and a 10 year old backing company with help on hand should you need it.