js-tutorial.dox

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/**
 * @page js-tutorial Using Flusspferd from Javascript
 *
 * It is possible to use Flusspferd without ever touching C++ - and even if
 * you do, you will probably use some of our Javascript-side features.
 *
 * @section Contents
 *
 * - @subpage js-tutorial-invoke
 * - @subpage js-tutorial-io
 * - @subpage js-tutorial-xml
 * - @subpage js-tutorial-getopt
 *
 * @see
 *   - @ref cpp-tutorial-modules
 */

/**
 * @page js-tutorial-invoke Using the Flusspferd shell / interpreter
 *
 * Once Flusspferd is @ref install "installed", you can run %flusspferd like
 * this:
 *
 * @verbatim
$ flusspferd
@endverbatim
 *
 * It will open up a shell. You can use it to evaluate arbitrary Javascript
 * expressions.
 *
 * @verbatim
> 1 + 1
2
> world = "Shell"; print("Hello", world);
Hello Shell
@endverbatim
 *
 * You can also invoke %flusspferd to run a Javascript file:
 *
 * @verbatim
$ flusspferd source.js
@endverbatim
 *
 * For more options, run <code>%flusspferd -h</code>.
 *
 * @section cmdarg Command line arguments
 *
 * Arguments given on the command line after the script name  are available as
 * a normal JavaScript array on the system module called @c args. For
 * example:
 *
 * @verbatim
#!/usr/bin/env flusspferd
function print_args(args) {
  // args.length is equivalent to argc in c
  print("There are", args.length, "argument(s)");

  for (var i=0; i<args.length; i++) {
    print(args[i]);
  }
}
var system = require('system');
print_args(system.args);

@endverbatim
 *
 * @section js-tutorial-emacs Using inferior-flusspferd-mode
 * Flusspferd comes with an
 * <a href="http://www.gnu.org/software/emacs/">Emacs</a> mode.
 * The Flusspferd mode can be used to interactively develop
 * javascript code by sending it to the Flusspferd shell.
 *
 * See \ref emacs-install "Emacs Mode install instructions"
 * on how to use it.
 *
 * Next: \ref js-tutorial-io
 *
 */

/**
 * @page js-tutorial-io Using io
 *
 * Previous: \ref js-tutorial-invoke
 *
 * There is an I/O function that you have probably already encountered:
 * @c print.
 *
 * @verbatim
> print("OK: ", [1,2,3,4])
OK: 1 2 3 4
> require("system").stdout.print("Same.")
Same.
@endverbatim
 *
 * In fact, @c print is a short form for the latter syntax. However, the print
 * abbreviation is not available in modules. To spare you the hassle of typing
 * require("system").stdout.print everytime, you can assign the module to a
 * variable.
 *
 * @verbatim
const sys = require("system");
sys.stdout.print("Works!");
@endverbatim
 *
 * The other global function that is exposed as part of @c prelude.js is
 * @c readLine - which reads a line from standard input.
 *
 * @verbatim
> readLine().substr(1)
abcd
bcd
@endverbatim
 *
 * (Where @c abcd is input.)
 *
 * Again, @c readLine is just an alias for @c require("system").stdin.readLine.
 *
 * The @c system module exposes three streams by default:
 *
 * - @c stdin
 * - @c stdout
 * - @c stderr
 *
 * There are many more things that you can do with this and the 'io' module,
 * see <a href="js/IO">the documentation for <code>io</code></a>.
 *
 * Next: \ref js-tutorial-xml
 *
 */

/**
 * @page js-tutorial-xml Using XML
 *
 * Previous: \ref js-tutorial-io
 *
 * Let us begin by loading an XML document from Jeni Tennison's website:
 *
 * @verbatim
> XML = require("XML")
> doc = XML.parse("http://www.jenitennison.com/index.xml")
<?xml version="1.0" encoding="UTF-16"?>
<?xml-stylesheet type="text/xsl" href="resources/style/page.xsl"?>
<my:doc xmlns:my="http://www.jenitennison.com/" xmlns="http://www.w3.org/1999/xhtml" ...>
  ...
</my:doc>
@endverbatim
 *
 * @note You may notice the encoding of UTF-16 above, because @c doc.toString()
 *       (which is implicitly called here) converts to a Javascript string, and
 *       in Javascript, strings are encoded in UTF-16, internally.
 *
 * Now let's look at that document in a few basic ways.
 *
 * @verbatim
> doc.rootElement
ELEMENT:doc
> doc.rootElement.firstChild = null // => delete document contents
null
> doc
<?xml version="1.0" encoding="UTF-16"?>
<?xml-stylesheet type="text/xsl" href="resources/style/page.xsl"?>
<my:doc xmlns:my="http://www.jenitennison.com/" xmlns="http://www.w3.org/1999/xhtml" ... />
> doc.firstChild
PI:xml-stylesheet
> doc.type
DOCUMENT
@endverbatim
 *
 * Or, leveraging XPath:
 *
 * @verbatim
> doc = XML.parse("http://www.jenitennison.com/index.xml")
...
> xpath = new XML.XPath(doc, {my: "http://www.jenitennison.com/"})
[object NativeObject]
> xpath.ns.html = "http://www.w3.org/1999/xhtml" // now, namespaces html and my can be accessed
http://www.w3.org/1999/xhtml
> links = xpath("//my:links/my:link")
ELEMENT:link,ELEMENT:link,ELEMENT:link,ELEMENT:link
> links.forEach(function(x) { print(x.getAttribute("href"), x.content); })
www.w3.org/XML W3C XML Page
www.xml.com XML.com
www.xml.org XML.org from OASIS
www.bayes.co.uk/xml Chris Bayes' XML Portal
@endverbatim
 *
 * @note Reference documentation has not been written yet.
 *
 * Next: \ref js-tutorial-getopt
 *
 */

/**
 * @page js-tutorial-getopt Using Getopt
 *
 * Previous: \ref js-tutorial-xml
 *
 * Flusspferd provides with getopt a module to parse command line parameters.
 * The module has a C++ and a Javascript API and is also used by the
 * Flusspferd Shell. See flusspferd::getopt for the reference.
 *
 * Getopt is similar to alternatives known from other languages, like
 * <a href="http://man.cx/getopt(3)">getopt(3)</a>. The getopt function
 * takes a specification which options are supported and returns a list of
 * parsed options. If no second parameter containing an Array of command line
 * input is passed it is read from the environment.
 *
 * The parameter specification is an object consisting of parameter names as properties.
 * Those properties contain objects defining different aspects of the parameter. So the
 * specification is basically a JSON structure. A very simple specification thus might look
 * like this:
 *
 * @verbatim
var spec = {
  "help" : { },
  "version" : { },
  "foo" : { },
  "bar" : { }
};
@endverbatim
 * 
 * getopt uses the following syntax for command line parameters:
 *
 * Short option (one character long): @p -S
 * 
 * Long option: @p --longoption
 *
 * If an option is short or long is determined by the length of the name. In our example all options
 * are long options. It is recommended to always provide a descriptive long option and provide a short
 * alias for common options. This brings us to the next point: Providing aliases. You can define several
 * aliases for each option by adding an @p "alias" option to the subobjects:
 *
 * @verbatim
var spec = {
  "help" : {
     "alias" : "h"
  },
  "version" : {
     "alias" : "v"
  },
  "foo" : {
     "alias" : ["f", "F"]
  },
  "bar" : {
     "alias" : ["baz", "b" ]
  }
};
@endverbatim
 *
 * getopt also supports arguments to those options. The following syntaxes are supported:
 *
 * Short option with argument: @p -Sargument or @p -S @p argument
 *
 * Long option with argument: @p --longoption=argument or @p --longoption @p argument
 *
 * You can specify that an option requires an argument with an @p "argument"
 * parameter which should be either @p "none", @p "optional" or @p "required"
 * and you can define an argument type with @p "argument_type".
 * The @p "argument_type" is currently useful to improve the help output and
 * for a bash completion script. We get back to this later.
 *
 * @verbatim
var spec = {
  "help" : {
     "alias" : "h"
  },
  "version" : {
     "alias" : "v"
  },
  "foo" : {
     "alias" : ["f", "F"],
     "argument" : "required",
     "argument_type" : "file"
  },
  "bar" : {
     "alias" : ["baz", "b" ],
     "argument" : "optional"
     // an argument_type does not need to be set
  }
};
@endverbatim
 *
 * Now we can parse the command line parameters with getopt:
 *
 * @verbatim
var getopt = require('getopt');
var result = getopt.getopt(spec);
@endverbatim
 *
 * @p result now is an object containing the parsed options as property names
 * which contain a list of arguments:
 *
 * @verbatim
{
  "option0" : [ "arg0", "arg1" ],
  "option1" : [ "arg0" ],
  "_" : [ "rest" ]
};
@endverbatim
 *
 * The property @p "_" is a special case containing the unparsed arguments.
 *
 * Now you could process result. But getopt provides an even easier way by using
 * callbacks. You can define callbacks inside the specifications:
 *
 * @verbatim
var spec = {
  "help" : {
    "alias" : "h",
    "callback" : function() {
      print("help");
      quit();
    }
  },
  "version" : {
    "alias" : "v",
    "callback" : function() {
      print("Version 1.0");
      quit();
    }
  },
  "foo" : {
     "alias" : ["f", "F"],
     "argument" : "required",
     "argument_type" : "file",
     "callback" : function(name, argument) {
       print("option '" + name + "' argument '" + argument + "'");
     }
  },
  "bar" : {
     "alias" : ["baz", "b" ],
     "argument" : "optional",
     "callback" : function(name, argument) {
       if(argument) {
         print("option '" + name + "' called with argument '" + argument + "'");
       }
       else {
         print("option '" + name + "' called without argument");
       }
     }
  }
};
@endverbatim
 *
 * @p "help" is a common option and every program using command line options
 * should provide it to list the supported options. getopt can even help
 * with this option since getopt already know the supported options. There is
 * a getopt_help function taking the parameter specification and generating a
 * corresponding output. To improve the output you should add a @p "doc"
 * property to all options.
 *
 * @verbatim
var spec = {
  "help" : {
    "alias" : "h",
    "doc" : "Displays this message.",
    "callback" : function() {
      print("usage: getopt-example.js [OPTIONS] ...");
      print(getopt.getopt_help(spec));
      quit();
    }
  },
  "version" : {
    "alias" : "v",
    "doc" : "Show version number.",
    "callback" : function() {
      print("Version 1.0");
      quit();
    }
  },
  "foo" : {
     "alias" : ["f", "F"],
     "argument" : "required",
     "argument_type" : "file",
     "doc" : "Foo!",
     "callback" : function(name, argument) {
       print("option '" + name + "' argument '" + argument + "'");
     }
  },
  "bar" : {
     "alias" : ["baz", "b" ],
     "argument" : "optional",
     "doc" : "Bar is the way to go.",
     "callback" : function(name, argument) {
       if(argument) {
         print("option '" + name + "' called with argument '" + argument + "'");
       }
       else {
         print("option '" + name + "' called without argument");
       }
     }
  }
};
@endverbatim
 *
 * getopt even provides functions to auto generate parts of a manpage
 * (flusspferd::getopt_man) and bash completion script
 * (flusspferd::getopt_bash).
 *
 * See @p help/getopt-example.js or @p misc/replace-var.js for examples on
 * the usage of getopt with Javascript or take a look at
 * @p src/programs/flusspferd.cpp for the getopt usage with C++.
 *
 */