I am a beginner in Javascript, I decided to practice Javascript by problem solving using it, I found an online judge that accepts Javascript V8 4.8.0 code.
So, I searched online to get that version of Javascript V8 on my machine, but I couldn't find any easy way, All the pages were explaining how to build it, and it seems to be a process that I don't need to go through.
Is there an easy way to compile and run command line apps written in Javascript on my machine?
Note: I don't want to use node.js because I tried using it's I/O and
as a beginner I think it is complex in some way.
Update: I found that package manager pbox.me which provides a version of V8 JavaScript Engine and I managed to install it.
Yet another problem appeared: whenever I try to run a js file writing d8 myfile.js in command line nothing happens as if it is an empty program, knowing that I tryied to d8.exe file and it is working, and I made sure the PATH is inserted in the environment variables.
What am I doing wrong?
The easiest way to get started with JavaScript is probably to use it in a browser. You can type simple things directly into the browser's JavaScript console (check the menu); or you can embed your code in a simple HTML document.
If you want, you can even pretty easily implement the readline()/print() functions, so you can pretend to be doing stdin/stdout based I/O: just read from an array of strings, and send output to console.log (or create DOM nodes if you want to be fancy and/or learn how to generate dynamic website content by hand).
Side note: V8 4.8 is severely outdated, don't use it to execute code you haven't written yourself.
I am practicing online programming contest held by codeforces, and I try to play javascript with it. However, I find it very difficult to setup my environment for offline test, they have readline() for input to stdio and print()/write() for output in stdout. Any help? Thanks.
For practising Javascript, you could use any thing from the chrome development console to online editors like JSFiddle. Nodejs allows you to run Javascript (which is used for client side rendering) on a server. What this means is that using node, you could run javascript on your terminal. As for the input , output functions you mentioned, it is easy to require them as node modules or use appropriate Javascript libraries for the same.
I'm working with a tool that only allows for Javascript as the scriptting language. With the script, I need to launch a process. How would I go about this?
The javascript code is running on the client that will launch the process. The javascript interpeter is RhinoJS.
So my question remains:
1. Is there a way that I can call a specific Java class from Rhino [ProcessBuilder]?
or
2. Is there a way to launch an executable from Javascript? [I've tried the UniversalXPConnect route, but it turns out that the version of Rhino I'm using doesn't really worry about permissions]
That was quick [I found the answer right after I asked]:
var pb = new java.lang.ProcessBuilder("notepad.exe", "c:\test");
pb.start();
Basically RhinoJS has a quirk to allow it to directly access Java functionality. So basically once should just launch the process from there.
Looking forward towards excellent javascript ctags support kept me thinking if a project like http://zombie.labnotes.org/ could be used to setup ctags to keep a vim user happy.
Hum, none of the projects you are citing are parsers or have anything to do with ctags.
PhantomJS let's you run your script as if it was run by a webkit-based browser. It won't output an analysis of your code, it will just execute it. You can use it to do a toSource() or a isPrototypeOf() on a function but that would be rather pointless.
JSDOM is an implementation of the DOM to use within your script. It can't be run as an external tool so it can't be used to generate tags or analyse your code.
Zombie.js is a testing framework that simulates a browser for you. Like JSDOM, it can't be run as an external tool and it has no ability to analyse your code.
You can feed your current script to phantomjs with :!phantomjs % or use zombie or jsdom in your script but none of it will help you have a better idea of the structure of your code or jump to the definition of a method.
However, if you use either zombie or jsdom or whatever other library in your project you can generate their respective tags files and add them to your .vimrc like this:
autocmd FileType javascript set tags+=path/to/a/library/tags
autocmd FileType javascript set tags+=path/to/another/library/tags
If what you want is a better/more modern tags generation you can try DoctorJS' jsctags or look at this thread for a more hackish way to make ctags work for you. As far as I know, these are you only options right now.
Given a need to write command line utilities to do common tasks like uploading files to a remote FTP site, downloading data from a remote MySQL database etc.
Is it practical to use JavaScript for this sort of thing? I know there are JavaScript interpreters that can be run from the command line, but are there libraries for things like FTP and database access the way there are for e.g. Java? If so, what's the best place to look for them? (Google searches with JavaScript in the keywords always seem to return many pages of browser specific things.)
And is there a way to package a JavaScript program up as a standalone executable on Windows?
Update: I've decided Python is a better tool for this kind of job, but the answers to the original question are still good ones.
Standalone executable?
By the way you ask the question, I'm not sure if you are aware, but the Windows Script Host - included in Windows - allows you to run .js files from the command-line. Your javascript will not be an executable, it will remain a script, a text file. The script runs within cscript.exe, which is provided by WSH. There's no compilation required. Maybe you knew all that.
I use Javascript this way for various utilities on Windows.
I think your instinct is right on the availability of libraries. You are sort of on your own to find all those things. Although, once you find them, it's not hard to package Javascript libraries as COM components and allow re-use from anywhere. See here for an example of packaging the Google Diff/Patch/Match Javascript library in COM.
Addendum: Once a bit of code is available within COM, it can be consumed by any Javascript running on the machine. Some examples of COM objects available to Javascript scripts running in WSH:
MSXML2.XMLHTTP object - used in AJAX, but can be used for any HTTP communication. There also an object for the XSLT engine so you can do transforms from script.
Excel.Application - allows you to open up Excel spreadsheets and automate them from Javascript.
Communicator.UIAutomation - automate MS Communicator (send IM's via script)
COM objects for Google Earth.
SlowAES - an all-Javascript implementation of AES encryption.
You can use Rhino to compile Javascript into Java byte code, and get access to all Java libraries.
Or you could use JScript.net, and get access to the .net libraries. .net includes a jsc.exe that produces exe-files.
Both of these requires the respective framework to be installed to be able to run.
Node.js is by far the best environment for running non-browser JS. I've used Rhino and SpiderMonkey, and there's a pretty huge difference in everything from the basics like how errors are handled to the size of the community using the tool. Node is pitched for "server-side" JS - building server apps in JS. It's great for this. But it works equally well for building command line tools.
The NPM package manager (bundled with Node) provides a nice global directory for finding and installing packages. It works much better than other language equivalents like PECL / Pear / CPAN / etc. Several high quality tools like JSHint, The Jade templating language, and the CoffeeScript compiler are all already available through NPM/Node:
npm install -g jshint, coffee-script, jade
jshint my_code.js
jade < my.jade > my.html
For args parsing, there are packages like commander.js. I currently use a heavily extended version of Commander in my underscore-cli command-line tool.
For messing with JSON or for doing command-line JS work (similar to "perl -pe"), check out underscore-cli - It's a really powerful tool for processing JSON data, processing underscore templates, and running JS expressions from the command-line. I use it for 1001 different things that would otherwise be really annoying to accomplish.
Rhino is bundled with JDK 1.6, jrunscript.exe in the bin directory will allow you to run any Javascript you want. Since it runs under Java you get access to any Java libraries that you may have.
We use it from the command line extensively. It's very good at that.
One way is to write these utilities as AIR applications - They can be written in JavaScript and need not have a UI. They have access to the command line, and there are existing ActionScript 3 libraries that can handle FTP etc. These ActionScript APIs can be called from JS, in AIR applications. AIR applications also have access to a sqlite database.
jslibs is a good standalone JavaScript runtime that support many 3rd party open source libraries like zlib, SQLite, NSPR, libiconv, libTomCrypt, OpenGL, ...