Posts Tagged javascript

Shell without ssh or root on your shared hosting

My site jcubic.pl is on shared hosting that don’t have ssh, and I wanted to have a shell access, so using my jQuery Terminal, I’ve stared a project leash. It’s a shell written in javascript with help from php and python cgi. It will give you a shell access, no need to install any new software, and you don’t need to be root (like with other shells like shell in a box, AjaxTerm or Buterfly).

, , , ,

Leave a comment

Using exceptions to simulate tail recursion in JavaScript

JavaScript is very powerful language but it don’t have tail call elimination. But it turn out that you can simulate it using exception system. Here is very simple recursive function that calculate factorial:

function factorial(n) {
    function recur(n, result) {
        if (n == 0) {
            throw result;
        } else {
            recur(n-1, result*n);
        }
    }
    try {
        recur(n, 1);
    } catch(e) {
        return e;
    }
}

It turn out that in JavaScript (I read that in Douglas Crockford book JavaScript: The Good Parts) you can use any expression in throw and it will be send to variable in catch statement.

So what the above code does it simple exit from the recursive loop and pass result to catch statement. And this is exactly what tail recursion is, in language scheme this happen by default when inner function (you also need to create inner function in scheme) have recursive call as last expression. Here is scheme version of tail recursive factorial:

(define (factorial n)
  (let recur ((n n) (result 1))
     (if (= n 0)
        result
        (recur (- n 1) (* result n)))))

the code use named let but it can be rewriten with inner function and invocation. (this kind of trick is needed in script-fuGimp extension based on scheme).

, ,

6 Comments

Add methods to Number object in JavaScript

In JavaScript everything is an object, even functions and numbers, and all objects even functions are first class citizens (which allow functional programming).

So this mean that you can call methods over numbers, and you can add new methods using Number.prototype. Here is example of range functions similar to that from Python, but bit different. (Python one return number from n to m – or from 0 to n – but this one return n numbers (n is this) starting from number passed as argument)

Number.prototype.range = function(n, result) {
    result = result || [];
    n = typeof n === 'undefined' ? 0 : n;
    if (this <= 0) {
        return result.reverse();
    } else {
        return this.range.call(this-1, n, result.concat([this-1+n]));
    }
};

And you can call this function/method using:

10..range(1)

It will return array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].

Note that there are two dots, it’s because when you use one it’s interpret as float number and thorw exception "SyntaxError: Unexpected token ILLEGAL" because it wait for a digit as next character.

Using this you can write factorial using

10..range(1).reduce(function(a, b) { return a*b; });

reduce function was added to Array.prototype in ECMAScript 5, You can check what browsers support them in this page.

You can wrap that code with a function and you can add it as Number prototype

Number.prototype.factorial = function() {
    return this.range(1).reduce(function(a, b) { return a*b; });
};

You can call it as:

10..factorial();

Here is example of times function (similar to that from Ruby)

Number.prototype.times = function(fn, self) {
    return this.range().forEach(fn, self);
};

You can use this function using:

10..times(function(i) { console.log(i); });

Leave a comment

Image color picker in javascript that work without canvas in every browser

If you want to create color picker from image in javascript you probably will use canvas, but what if you need it work in IE as I needed. You can use some server side help to fetch pixels data from the server. I use php for that and GD library. The code is below.

cross-browser color picker

Server side code that return json pixel data


<?php

function rgb($color) {
    $result[] = ($color >> 16) & 0xFF;
    $result[] = ($color >> 8) & 0xFF;
    $result[] = $color & 0xFF;
    return $result;
}

function imagecreatefrom($filename) {
    $path = pathinfo($filename);
    switch($path['extension']) {
        case 'png':
            return imagecreatefrompng($filename);
        case 'jpg':
            return imagecreatefromjpeg($filename);
        case 'gif':
            return imagecreatefromgif($filename);
        default:
            return null;
    }
}

function getImageData($filename) {
    list($width, $height) = getimagesize($filename);
    $image = imagecreatefrom($filename);
    $image_data = array();
    for ($y = 0; $y < $height; ++$y) {
        $row = array();
        for ($x = 0; $x < $width; ++$x) {
            $row[] = rgb(imagecolorat($image, $x, $y));
        }
        $image_data[] = $row;
    }
    return $image_data;
}

if (isset($_GET['filename'])) {
    $filename = $_GET['filename'];
    if (file_exists($filename)) {
        $result = array(
            'error' => null,
            'result' => getImageData($filename)
        );
    } else {
        $result = array(
            'error' => "The file '$filename' don't exist",
            'result' => null
        );
    }
} else {
    $result = array(
        'error' => "You need to put filename",
        'result' => null
    );
}
header('Content-Type: application/json');
echo json_encode($result);

?>

Then you can fetch the data using ajax and add get invidial pixels on mousemove


    var img = $('img');
    $.getJSON('image_data.php', {filename: img.attr('src')}, function(data) {
        if (data.error) {
            alert(data.error);
        } else {
            $('.eyedropper').click(function() {
                picker = true;
                return false;
            });
            img.mousemove(function(e) {
                if (picker) {
                    var x = Math.round(e.pageX - offset.left);
                    var y = Math.round(e.pageY - offset.top);
                    if (x >= 0) {
                        $('.color').css('background-color',
                                        'rgb('+data.result[y][x].join(',')+')');
                    }
                }
            }).click(function(e) {
                picker = false;
            });
        }
    });

Now all you need to have is element with class eyedropper like a link in your html:


<a href="#" class="eyedropper">pick the color</a>

, ,

3 Comments

How To Add Translation Feature To Twitter

I don’t know about you but, I follow few peple that sometimes tweet in different language then English. And English is the only foreign language I know. So if I want to see what they tweet about sometimes I use google translate to read the content.

I always thought that it will be nice feature for Twitter to have translate button, so I created one, using WebSockets and Ruby.

So how I did this, first I downloaded websockets ruby library from github web-socket-ruby, I already had translation script written in Ruby that use google translate, so I added websocket server to it.

#!/usr/bin/ruby

require 'net/http'
require 'uri'
require 'optparse'
require 'json'
require 'socket'
require 'web_socket'

class NotConnectedException < Exception
end

def server(port, domains)
  server = WebSocketServer.new(
    :accepted_domains => domains,
    :port => port)
  puts("Server is running at port %d" % server.port)
  server.run() do |ws|
    puts("Connection accepted")
    puts("Path: #{ws.path}, Origin: #{ws.origin}")
    if ws.path == "/translate"
      ws.handshake()
      while data = ws.receive()
        printf("Received: %p\n", data)
        data = JSON.parse(data)
        response = translate(data['text'], nil, data['to_lang']).join("\n")
        ws.send(response)
        printf("Sent: %p\n", response)
      end
    else
      ws.handshake("404 Not Found")
    end
    puts("Connection closed")
  end
end

def escape(o)
  o.gsub(/([^ a-zA-Z0-9_.-]+)/n) {
    '%' + $1.unpack('H2' * $1.size).join('%').upcase
  }.tr(' ', '+')
end

def translate(text, from=nil, to=nil, cookie=nil)
  url = URI.parse("http://translate.google.com/translate_a/t")
  query = "?hl=en&client=t&text=#{escape(text)}&multires=1&otf=1&pc=0&sc=1&ie=UTF-8&oe=UTF-8"
  query += "&sl=" + (from ? from : 'auto')
  if to
    query += "&tl=#{to}"
  end
  begin
    http = Net::HTTP.new(url.host)
    res = http.get(url.path + query)
    res.response['content-type'] =~ /charset=(.*)/
    charset = $1
    JSON.parse(res.body.gsub(/,{2,}/, ',').gsub(/,\]/, ']'))[0].map {|i|
      # google sometimes put spaces around numbers
      i[0].gsub(/\{ *([0-9]) *\}/, '{\1}')
    }
  rescue NoMethodError
    raise NotConnectedException
  rescue SocketError
    raise NotConnectedException
  rescue 
  end  
 
end

def msg(str, type='info')
  system("zenity --#{type} --title='translation' --text='#{str}'")
end

params = ARGV.getopts('i:o:gcsp:')

def error(msg, gui=false)
  if gui
    msg(msg, 'error')
  else
    puts msg
  end
end

def usage()
  puts "usage:"
  puts "translate [-i <INPUT LANG>] -o <OUTPUT LANG> [MORE OPTIONS]"
  puts "-g - show zenity dialog"
  puts "-c - get input from clipboard"
  puts "-s - run as server"
  puts "-p - server port"
end

begin
  if params['s']
     begin
       server(params['p'] ? params['p'].to_i() : 8080, 'twitter.com')
     rescue Interrupt
       puts "Server Exit"
     end
  else
    if params['c']
      input = `xclip -o -sel clip`
    else
      input = ARGF.read()
    end
    translation = translate(input, params['i'], params['o'])
    if params['g']
      msg(translation.join(". "))
    else
      translation.each{|sentence|
        if sentence != ''
          puts sentence
        end
      }
    end
  end
rescue JSON::ParserError => e
  error("Response Error: " + e.message, params['g'])
rescue NotConnectedException
  error("sorry but it seems that your internet connection is down", params['g'])
end

Then I created this bookmarklet. (I notice that profile page use jQuery.noConflict() so I can’t access it from bookmarklet. So here is updated code that insert jQuery script again – in use continuation to block execution of the script until jQuery is loaded). To use bookmarklet just copy code below and insert into url address bar when twitter tab is active

javascript:(function(continuation) {
    function attr(elem, key, value) {
        elem.setAttribute(document.createAttribute(key, value));
    }
    var script = (function() {
        var head = document.getElementsByTagName('head')[0];
        return function(src) {
            var script = document.createElement('script');
            script.setAttribute('src', src);
            script.setAttribute('type', 'text/javascript');
            script.setAttribute('async', 'false');
            head.appendChild(script);
            return script;
        };
    })();
    script('https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js');
    var interval = 100;
    setTimeout(function() {
        if (jQuery) {
            continuation(jQuery.noConflict());
        } else {
            setTimeout(arguments.callee, interval);
        }
    }, interval);
})(function($) {
    function translator(fun, lang) {
        var socket = new WebSocket("ws://localhost:8080/translate");
        socket.onopen = function() {
            console.log("Socket has been opened!");
        };
        socket.onclose = function() {
            console.log("closed");
        };
        return fun(function(text, respond) {
            socket.onmessage = function(msg) {
                respond(msg.data);
            };
            var data = JSON.stringify({to_lang: lang, text: text});
            socket.send(data);
        });
    }
    var translate_tweet = translator(function(translate) {
        return function(content) {
            var tweet_container = content.find('.js-tweet-text');
            var tweet = tweet_container.html();
            content.data('original', tweet);
            var links = [];
            var i = 0;
            tweet = tweet.replace(/<a[^>]+>[^<]+<\/a>|<a[^>]+><s>(#|@)<\/s><b>[^<]+<\/b><\/a>/g, function(link) {
                links.push(link);
                return '{' + i++ + '}';
            });
            translate(tweet, function(result) {
                for (var i=links.length; i--;) {
                    result = result.replace('{' + i + '}', links[i]);
                }
                tweet_container.html(result);
                var actions = content.find('.tweet-actions');
                if (actions.find('.action-orig-container').length == 0) {
                    actions.append('<li class="action-orig-container"><a href="#">Original</a></li>');
                }
            });
        };
    }, prompt('Select Language: af - afrikaans, sk - albánskej, ar - عربي, be - Беларускі, bg - Български, zh - 荃湾, zh - 太阳, hr - Hrvatski, cs - Český, da - Danske, et - Eesti, tl - filipiński, fi - Suomi, fr - Français, gl - galijski, el - Ελληνικά, iw - עברית, hi - हिन्दी, es - Español, nl - Nederlands, id - indonezyjski, ga - Gaeilge, is - Íslenska, ja - 日本語, yi - ייִדיש, ca - Català, ko - 한국의, lt - Lietuvos, lv - Latvijas, mk - Македонски, ms - Melayu, mt - Malti, de - Deutsch, no - Norsk, fa - فارسی, pl - polski, ru - Русский, ro - Română, sr - Српски, sk - Slovenský, sl - Slovenski, sw - Swahili, sv - Svenska, th - ภาษาไทย, tr - Türk, uk - Український, cy - walijski, hu - Magyar, vi - Việt, it - Italiano'));
    $('.content').unbind('mouseover').live('mouseover', function() {
        var $this = $(this);
        if ($this.find('.action-trans-container').length == 0) {
            $this.find('.action-fav-container').
                after('<li class="action-trans-container"><a href="#">Translate</a></li>');
        }
    });
    $('.action-orig-container').unbind('onclick').live('click', function() {
        var content = $(this).parents('.content');
        content.find('.js-tweet-text').html(content.data('original'));
        content.find('.action-orig-container').remove();
        return false;
    });
    $('.action-trans-container').unbind('onclick').live('click', function() {
        translate_tweet($(this).parents('.content'));
        return false;
    });
});

CODE LICENSE: you can use the code for whatever purpose you like it’s realeas on Sharing Agreement.

, ,

2 Comments

Really wicked web application source code hiding

I saw this video on YouTube from DefCon Conference.

I go to samy website, and it’s web application which look like Microsoft Windows. So first think I do to see how it is build. I look at source code and it’s look like there is no code at all, but in the middle (line 281) there is this

<script>/*
No source for you!
*//
</script>

Before and after script tags are only empty lines (\n), I check the end of the line 283 and there is following code (line breaks and indentations are mine):

/.source.replace(/.{7}/g,function(w){document.write(
    String.fromCharCode(parseInt(w.replace(/ /g,'0').
                                 replace(/	/g,'1'),2)))});

And thats it. So where is the real code? And the answer is this:

  1. He encode all characters in html as binary and replace zeros as space and ones as tabulations. there is no string, but in 283 line there is this: "*//" which is the end of multi-line comment and beginning of Regular Expression (which look like simple closing comment)
  2. He get value of the string representation of the RegEx using source field
  3. replace all whitespace with '0' and '1'
  4. convert it to decimal
  5. get the value of characters encoded and print all of that out

Pretty clever.

Of course you can get generated code from a menu “View Generated Source” from WebDeveloper toolbar in Firefox or see the the DOM in Firebug.

, , ,

Leave a comment

jQuery splitter – split container

This is my latest jquery plugin — “splitter” which splits content vertically or horizontally with movable element between them, that allow to change the proportion of two element. You can get it from github. The demo is here.

, ,

21 Comments

JQuery Terminal Emulator Plugin

My new project JQuery Terminal Emulator. It’s a plug-in which can be used to add Command Line interface to your application. You can use it to easily create server configuration tool or can be help in debugging or testing server side of AJAX applications. You can put lots of options in one place.

You can create command line interface to JSON-RPC in one line of code. Just set the path to rpc service.

$(document.documentElement).terminal("json-rpc-service.php");

If you want to use authentication.

$(document.documentElement).terminal("json-rpc-service.php", {
    login:true
});

And when user type user and password it will call login rpc method, get the token and pass that token to all methods on the server when user type command. So when user type for example add-user foo foo@bar.com it will call json-rpc add-user with parameters [token, "foo", "foo@bar.com"].

, , ,

1 Comment

Create nice looking blockquote with jquery and css

If you want to create nice looking blockquotes on your web page here is simple plugin.

nice looking blockquote

First basic css

.quote {
    font-size: 2em;
    font-family: Times New Roman, times, serif;
    position: relative;
}
.quote p {
    margin: auto;
    text-align: justify;
}
.quote span {
    font-size: 4em;
}
.quote span.open {
    position:absolute;
    top:-0.35em;
    left:0;
}
.quote span.close {
    position:absolute;
    bottom: -0.8em;
    right: 0;
}

code for the plugin

$.fn.quote = function(params) {
    $(this).addClass('quote');
    var width = params && params.width ? params.width : 400;
    $(this).css('width', width);
    $(this).html('<p>' + $(this).html() + '</p>');
    $(this).find('p').css('width', width - 120);
    $(this).append('<span class="close">&rdquo;</span>');
    $(this).prepend('<span class="open">&ldquo;</span>');
};

create basic html

<blockquote>Lorem ipsum dolor sit amet, consectetur 
adipiscing elit. Nulla sed dolor nisl, in suscipit justo. 
Donec a enim et est porttitor semper at vitae augue.
</blockquote>

And run the plugin

$(document).ready(function() {

    $('blockquote').quote({'width': 500});

});

The default width is 400 px

lt

, ,

Leave a comment

How to use and extend BiwaScheme

BiwaScheme is scheme implementation in Javascript.

Here you can find scheme interpeter using BiwaScheme (using JQuery Terminal Emulator inside JQuery UI Dialog). If you want to download BiwaScheme package click here.

BiwaScheme use prototype javascript library.

If you wat to use interpreter in your own code you must:

  • add this to head tag
    <script type="text/javascript" src="src/development_loader.js">
    </script>

    or if you want to make distribution you must have make and YUI Compressor which require java

    Uncomress package and type make in biwascheme directory it will create lib/biwascheme.js file which is compressed library. You must put it in head of your html file:

    <script type="text/javascript" src="lib/biwascheme.js">
    </script>
  • Create instance of Interpreter class
    var intepreter = new BiwaScheme.Interpreter();
  • You can also put function for error handling to the constructor
    var biwascheme = new BiwaScheme.Interpreter(function(e, state) {
        $('output')[0].innerHTML += e.message;
    });
    
  • If you want to result be proper displayed you must overwrite puts function
    var output = $('ouptut');
    function puts(str, no_newline) {
        if (no_newline) {
            output[0].innerHTML += str;
        } else {
            output[0].innerHTML += str + "<br />";
        }
    }
    
  • Evaluating funtion should look like this:
    var input = $('input');
    var output = $('output');
    function scheme_eval(e) {
        try {
            var code = input.html();
            // show trace messages
            if (trace) {
                var opc = interpreter.compile(code);
                var dump_opc = (new BiwaScheme.Dumper()).dump_opc(opc);
                output[0].innerHTML += dump_opc;
            }
            interpreter.evaluate(code, function(result) {
                if (result != undefined) {
                    result = BiwaScheme.to_write(result);
                    output[0].innerHTML += '> ' + result + "\n";
                }
            });
        } catch(e) {
             //this will never be evaluated because all errors are
             //pased to function pased to Interpreter constructor
             output[0].innerHTML += e.message;
             throw(e);
        }
    }
    
  • You could bind this function with onclick event
    $('eval_btn').click(scheme_eval);
  • If you want to define new function which will be accessable in your scheme interpreter you should use define_libfunc function from global object BiwaScheme. First parametr is scheme name of the function, second and third are minimum and maximum of parameters and fourth is the anonimus function with one argument which is array of parameters pased to scheme procedure.
    BiwaScheme.define_libfunc('env', 0, 0, function(args) {
            var result = new Array();
            for(fun in window.BiwaScheme.CoreEnv) {
                result[result.length] = fun;
            }
            // result should be converted from array to scheme list
            return result.to_list();
        });
    

    This function will return list of all function and variables in scheme global Environment.

    The following scheme function will display that list:

    (define (show-env)
      (let iter ((list (env)))
        (if (not  (null? list))
            (begin
               (display (car list))
               (newline)
               (iter (cdr list))))))

    or simplier.

    (define (show-env)
      (display (string-join (env) "\n"))
      (newline))
    
  • If you want to define some variable you must put it in BiwaScheme.CoreEnv array.

    If you want to define (in javascript) function with scheme code use BiwaScheme.define_scmfunc. First parameter is scheme name, second and third are minimum and maximum of parameters (BiwaScheme check this before function are evaluated) and the fourth one is string containing your scheme code (should be lambda expresion).

    BiwaScheme.define_scmfunc('**', 1, 1,
            "(lambda (x y) \
                 (cond \
                     ((= y 0) 1) \
                     ((< y 0) (** (/ 1. x) (- y))) \
                     (else \
                        (let iter ((i 1) (result x)) \
                           (if (= i y) \
                               result \
                               (iter (+ i 1) (* result x)))))))");

    Former function define power with tail recursion.

    You could also create scheme macro in javascript with BiwaScheme.define_syntax function. This function must return BiwaScheme.Pair object which will be evaluated. It accept single parameter which is scheme expression (tree build from BiwaScheme.Pair objects). This is example of using macros from javascript:

    //this is helper Array method which traverse a tree build with arrays 
    //and create tree of Symbols
    // it use to_list function wich is defined by BiwaScheme
    Array.prototype.to_tree = function() {
        for(var i in this) {
            if (this[i] instanceof Array) {
                return this[i].to_tree();
            }
        }
        return this.to_list();
    };
    
    BiwaScheme.define_syntax('foo', function(expr) {
        return [BiwaScheme.Sym("display"),
                [BiwaScheme.Sym("quote"), expr.cdr.to_array().to_tree()]
               ].to_tree();
    });
    

    This code create new macro foo which simply display expression passed as parameters. Note that the whole expression is in expr.cdr filed.

  • In interpeter you could also define macros (like common lisp macros) with define-macro expresion.
    (define-macro (for params . body)
        `(let iter ((,(car params) ,(cadr params)))
            (if (< ,(car params) ,(caddr params))
                (begin
                    ,@body
                    (iter (+ ,(car params) ,(if (= (length params) 4)
                                                (cadddr params)
                                                1)))))))
    

    The former code define for loop (which use tail recursion), you could use it with (for (variable init end step) code):

    (for (i 1 10)
      (display i)
      (newline))

    or

    (for (i 10 100 10) (display i) (newline))

    Which display numers: 10 20 30 40 50 60 70 80 90 100.

Update: Check also Extending Scheme interpreter in BiwaScheme wiki on GitHub.

,

10 Comments

Follow

Get every new post delivered to your Inbox.

%d bloggers like this: