I am learning javascript and other things used with it. I have read some links that talk about nodejs and underscore.js but I don't understand how they are related. I am not sure if they are related or not in the first place. I understand that underscore.js requires node.js to be pre installed. If underscore.js is a library then what is node.js? And what is the purpose of node.js. I am sorry if this is a stupid question. I am a beginner.
They are not really related (except that both are Javascript technologies).
underscore.js is a Javascript library, like jQuery. It provides frequently used functions for use in your Javascript code.
node.js is a Javascript engine, a program that is used to run Javascript. Just like you have programs to run Perl, Ruby or Python code. In the Javascript world, this is a bit unusual, as traditionally, you would not write "server-side" programs in Javascript. Instead, the Javascript would run in a web browser, as part of a web site. The code that produces the web site on the server would be written in Java, Perl, Python, Ruby or whatever. With node.js, you can have the "whole stack" in the same language.
underscore.js does not require node.js.
In the browser, you can simply load underscore.js. If you have a server-side program, it may be running on node.js, but it could also use other engines, and underscore.js does not care.
node.js is also used as the basis for "build tools" in the Javascript world (similar to "make" for C people, or Maven for Java folks). Those are programs that a library developer uses to package the code, generate documentation, run unit tests, etc. Maybe underscore.js uses node.js to build itself.
Let's take a step back.
JavaScript is a programming language.
You probably know it's used in the browser. Node.js takes JavaScript and makes it so you can create JavaScript programs on your computer.
Now, underscore.js is a JavaScript library which provides lots of nice capabilities to JavaScript. Not necessarily on the computer/server in Node.js, but perhaps in the browser. But wherever you add it, it adds those features.
So there you have it. Both are JavaScript. There are related only by that.
Related
There is c++ library and I need to make function calls to this library from JavaScript running on the browser on the client side, the library resides in the client machine only. How can I load the library and access the interfaces (functions) provided by the c++ library? The library contains algorithms and rendering calls mainly.
A few options I can think of:
1) Find a different library in JavaScript.
2) Port the C++ code over to JavaScript. How easy this is depends on
how complex the C++ code is or how much of it you need.
3) Wrap the C++ code in a web service on a server and call it using AJAX. I'm not personally familiar with any C++ web service frameworks, but barring that, you could create Java, Python, or .NET bindings for the library (or just for the portion that you need), or bindings in another language. Then you would write your web service in whatever language you chose.
3B) Alternative to #3 - If the library has a command-line interface, or if there exists a command-line program that uses the library, your web service could call that and you wouldn't have to write a language binding. Note however that there are performance & security problems to be aware of with this option.
4) If you have the C++ source code for the library, you could try to compile the library to JavaScript using Emscripten.
I would probably try those in that order, roughly. I might try #3 last cause it could be the trickiest.
Also, if you do #3 or #3B, you'll want to be sure your use of the library is thread-safe.
Disclaimer: I've never tried any of these except #3B.
You'd be better off creating a 'C' wrapper for the C++ library and calling that from the Javascript.
C++ is notoriously difficult to interface with due to the language standard lacking a tight ABI definition. C does not have this limitation. For this reason, 'C' ends up being the lingua franca when you want two programming languages to talk with each other.
Usually browsers doesn't allow that, because that's very insecure.
You might compile C++ in asm.js and use it as JavaScript library.
Alternatively you can create browser extension, which will run or call desired code.
Yes its possible but before you can call them from javascript. You do this by creating an interface file to tell javascript about the interface.
I saw this website: AppJS , and if you go to the end of it, you'll see the Section "We need your help!". Therein is explained that you could help by making wrappers for a specific platform (whichever you want, be it Windows, Linux, Mac...) that should be an interface for the JavaScript language so that the JavaScript can call those functions (and obviously to create cross-platform apps).
So my question is how can I write something in C++, compile it, and then call that function from outside, specifically from JavaScript?
What should I know? Does the AppJS or the NodeJS have some kind of module programmed that allows the communication between your own compiled C++ code and the JS part?
Basically how does this wrapping work?
Edit:
Probably, in the next couple of links there is information about the topic.
http://pravinchavan.wordpress.com/2013/11/08/c-binding-with-node-js/
http://es.slideshare.net/nsm.nikhil/writing-native-bindings-to-nodejs-in-c
Rather than "wrapping" the word that would fit the most would be "binding" I guess.
Pthread (POSIX) is a "wrapper" but not a "binding".
NodeJS is a library for V8, the Google open source JavaScript engine, written in C++. I think you should look into V8 for more information.
You need to create an addon with the help of v8 jscript, a c++ library and libuv, a C event loop library. Read more on
http://nodejs.org/api/addons.html
I have some C++ code that I want to expose to client side of a web app. Ideally, I want to write Javascript wrapper objects for my C++ classes so that I can use them clientside.
Has this been done before?. Does anyone have a link to show how this may be achieved?
There is a library to convert C++ code to javascript, it might help:
emscripten
Libjspp C++ template based wrapper for embedding and extending Javascript engine spidermonkey 1 . 8 . 5 and more
SpiderMonkey? is Mozilla Project's Javascript/ECMAScript engine.
Libjspp allows C++ developers to embed SpiderMonkey? simply and easily into their applications. Libjspp allows to run multiple Javascript Engines within same process which suits one engine per thread para dime which is helpful in achieving true parallisim. Also Libjspp no way stops user from running multiple threads within engine.
http://code.google.com/p/libjspp/
I guess that RPC is what you want. You'll need to wrap your functions on the server side using some sort of framework. I've not yet used it, but this one looks promising.
On the client side you use proxy objects to dispatch the function calls. The communication is handled usually either via XML-RPC or JSON-RPC. I used this client side framework and was quite content but I'm sure you'll find many others.
This is an old topi, however, I was in the exact situation right now, and all of the solutions I found on the net complicated or outdated.
Recently, I ran across a library which supports V8 engine (including the new isolation API, which makes 90% of the libraries I found outdated) and provides great exposure and interaction API.
https://github.com/QuartzTechnologies/v8bridge
I hope that my solution will help anybody.
There's a relatively new library for doing this called nbind. Maybe that would suit you? It looks very good to me, and I'm just about to start using it.
I think you want a C++ JSON parser. You should be able to find one here http://www.json.org/. It may not do all you want because it just serializes and deserializes C++ objects without any behavior, but it should be good enough. See https://stackoverflow.com/questions/245973/whats-the-best-c-json-parser for some discussion.
If the C++ code has to be on the client, then there is no simple way to do this for a web app. A solution may involve coding plugins for the browsers you want to support, which may then be accessed from javascript code.
If, for example, you need this for a client application, that is another case. Such a thing has been done and involves linking your application to (or running from outside) with for example chromium library, or any other javascript execution engine. That way you can create bindings to C++ classes and use such objects from javascript and vice-versa. Note that this is also not a trivial solution and may be a big effort to implement (also requires additional resources).
You could for example wrap the C++ classes in PHP or Python, and then implement an API over HTTP to access the required functions.
Or if you insist on exposing the functions as JavaScript you could try using Node.js, and create an C++ add-on to wrap you classes. See the Node.js documentation here: http://nodejs.org/api/addons.html#addons_wrapping_c_objects
But either way, I don't think avoid creating some sort of API (HTTP SOAP, XML RPC) to access the functions on your server.
Though QML is not exactly Javascript, Qt is not plain C++, but what they do together seem just like what you need
I'm now thinking to establish my server-side code in JavaScript, and begin to do all on it, but I want to know about its security and flexibility compared to PHP.
I want to know too, if it can be successfully used to develop things like forum boards, full web-sites and things like this, as PHP does.
Javascript is just now starting to get some presence on the server, with things like ServerJS and nodeJS, but right now, you would probably be best off using PHP for your server side code, and javascript for client-side beautification.
The question is very, very broad. Interpreting it as "can I use Javascript on the server":
Fundamentally, sure, Javascript is a very powerful language and so you can do development in it server-side just like you can client-side (and if you do client-side scripting as well, you get some definite reuse benefits using Javascript on the server).
For Apache systems, there's the v8cgi project (a FastCGI Javascript plug-in with connectors, using Google's freaky-fast V8 engine).
On Microsoft-based systems, IIS supports Javascript (JScript) on the server out of the box (I use that all the time), which has access to all of the ActiveX stuff (e.g., for talking to databases, dealing with the file system, etc.).
If your server framework is JVM-based, there's Rhino, which is Javascript for the Java platform and has access to all (or nearly all) of the libraries available for Java — e.g., a huge ecosystem of libraries and plug-ins.
Aside from v8cgi, there are a couple of other projects built on Google's V8 engine.
There's a place that does a full stack for you called chromeserver (I don't know what their backend is; I'm not going to infer from the name).
Paul mentioned ServerJS and NodeJS.
There's the whole CommonJS project.
Etc. etc. etc. There's quite a list on Wikipedia.
Arguing against, there's a very rich ecosystem built around PHP. Unless you're using something like Rhino for the Java platform or JScript on IIS (because of the ecosystems they leverage), you may find that you don't have nearly that ecosystem available to you when developing in Javascript for the server. I mean, if you're looking for pre-built forum or wiki software (for example), let's just say you can't swing a dead cat without finding one based on PHP, and the same cannot be said of Javascript on the server.
The way they are usually used, PHP and JavaScript run in entirely different worlds, and are not really comparable. (There is a server-side version of JavaScript but it's fair to say it's not especially widespread yet, and doesn't run on standard web hosting.)
The security issues you are going to encounter in JavaScript (on the browser) side are very different from what you have to look out for in PHP.
I want to know too, if it can be sucessfully used to develop things like forum boards, full web-sites and things like this, as PHP does.
No, not with client-side Javascript. For dynamic applications, you will always need some server-side language backing it, be it PHP or some other language like ASP, Python, Ruby, Perl....
To replace PHP with Javascript, you need server-side Javascript and there is a lot happening on that front. Mozilla’s Rhino runs Javascript atop the JVM and it seems Google is also working on its own server side Javascript framework. The most popular in-production implementations are:
Helma: Several active projects are using it, runs on Jetty & Rhino and lets developers leverage the power of JVM, has its own object-oriented MVC framework
Project Phobos: runs on Glassfish & Rhino and lets developers leverage the power of JVM, includes plug-ins for NetBeans and integrates with jMaki Web UI framework
JSSP: A very simple server side framework, a lot like classic ASP, JSP and PHP
Aptana’s Jaxer showed a lot of promise, especially by bringing the DOM to the server side, but the project seems dead now. From what I understand, node.js is not a server-side Javascript framework in the same sense as Helma and Phobos. Instead it can be used for writing event-driven servers in Javascript (for example: writing your own web server).
Yes, my site is written by node.js
Using websvr, it's Java style have filter and handlers, hosting on debian OS.
This is slightly off-topic, but it may actually get to the core of your question:
if you want to use only one language for web applications, you may wanna have a look at Haxe.
It is a cross-platform language, that (among other targets) compiles to JavaScript and PHP source as well as NekoVM bytecode. For server-side JavaScript, there are NodeJS bindings.
This way you are not bound to a specific platform. The neko and PHP APIs are largely compatible, so you can deploy on both platforms, having the option to choose neko's speed and persistency or PHP's ease of deployment. Please note however, the PHP output has a little overhead although common optimizers as eaccelerator will make this barely noticeable.
Haxe is significantly less forgiving than both JavaScript and PHP. This makes it harder to learn, but a much safer, robust and in the end more productive tool.
In a word: no. Javascript is a client-side language. In order to do the things that you are describing, you need a server-side language such as PHP.
EDIT: OK, technically it is possible to implement Javascript in other areas besides the browser, but this is not very common.
5 YEAR EDIT: Well, 5 years later, this answer obviously is not accurate, with the popularity of things like node.js. Let that be a testament to how quickly things can change!
PHP and JavaScript are two different languages that do two different things. One cannot replace the other. You are most likely going to use a combination of the two. JavaScript for client-side stuff. PHP for server-side stuff.
I am using GWT, which includes a Java-to-JavaScript compiler. Before this project, targeting the JavaScript runtime from a different language hadn't occurred to me, and I'm enjoying the GWT experience.
A quick search revealed Java2Script as another Java-to-JavaScript solution. Are there any other mature compilers that target the JavaScript runtime?
List of languages that compile to JS
You also have Haxe. It features static, structural, strong and inferred typing; algebraic data types; lambda expressions with closure support; a module system and can compile not only to JavaScript but also Flash, C++, Neko, PHP. Java support is under development too.
Pyjamas compiles Python to JavaScript.
HotRuby runs Ruby source code under JavaScript and Flash.
Orto is (was?) a JVM implemented in JavaScript. (Original site is down; link is to a blog entry.)
The ZK framework, which likes to compare themselves favorably against GWT, uses Java and XML to generate JavaScript. (They claim that it takes far less code than GWT to do the same stuff.)
And I have heard it well-argued that jQuery is a separate language that happens to be implemented in, and run under, JavaScript. :-)
OpenLaszlo is on open source XML -> Javascript (technically DHTML, also can compile to Flash) compiler. I've played with it a little bit and it seemed interesting, although have never used it seriously (bad IDE support when I tried it).
Objective-j is a similar project that resembles objective-c, although runs as javascript (not sure if it compiles it or has a js interpreter). I don't know much about it, but do see posts about it on the Ajaxian from time to time.
Parenscript is "a translator from a small Lispy language to JavaScript". It's not Common Lisp -- it's mostly just Lisp syntax for Javascript, though for simple things you can write the same code to target both, if you're careful. I'm not sure I'd call it "mature", either.
While there are other products which compile to javascript (noted in the other comments), I believe that GWT is, by far, the most mature one out there, in terms of real-world usage.
The simple fact that a number of Google's core applications use GWT (e.g.: the new adwords GUI, Google wave, etc) means you can have confidence the product is going to be maintained for at least the next few years, it isn't just going to fade away anytime soon.
Another thing to keep in mind is that GWT is far more than a java-to-javascript compiler, it also is an optimizing compiler, it has hosted mode, it is fully interoperable with native javascript, it does image bundling, it does code spliting in the new version, etc.
Script #
JSC
cappuccino (sort of)
The inventors of Clojure (a JVM based Lisp dialect) launched ClojureScript in mid-2011. ClojureScript compiles Clojure source code into JavaScript, making use of the Google Closure compiler and the Closure framework. ClojureScript code can run both in the browser client, or on node.js servers.
Here's a shameless plug for a project I started and am continuing to develop: scxml-js, a Statecharts-to-JavaScript compiler