need help understanding this code.

Discussion in 'Javascript' started by Elmbrook, Sep 28, 2003.

  1. Elmbrook

    Elmbrook Guest

    Hi,

    I've been trying to figure out this javascript code used here (this code is
    used for supplying browser info to a tracking company):

    In particular I'm trying to understand this line:
    EXd=document;EXw?"":EXw="na";EXb?"":EXb="na";
    and this one: EXd.write("<img
    src=\"http://t0.extreme-dm.com","/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&
    ","l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->

    Why do they have a variable j=y defined? There is no 'j' variable defined
    in the code.

    If I modify the http://t0.extreme-dm.com and send the results to my ASP page
    and use Querystrings to see what the values are, I only get the Screen width
    and colour depth values. The referrer information is not showing. I also
    don't understand how they can extract users country domain from this code.

    Thanks
    Tristan
    www.backpackpro.com


    ----------- Complete code below ---------------


    <a target="_top" href="http://t.extreme-dm.com/?login=abc"> <img
    src="http://u1.extreme-dm.com/i.gif" height=2
    border=0 width=2 alt=""></a>
    <script language="javascript1.2"><!--
    EXs=screen;EXw=EXs.width;navigator.appName!="Netscape"?
    EXb=EXs.colorDepth:EXb=EXs.pixelDepth;//-->
    </script>
    <script language="javascript"><!--
    EXd=document;EXw?"":EXw="na";EXb?"":EXb="na";
    EXd.write("<img src=\"http://t0.extreme-dm.com",
    "/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&",
    "l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->
    </script>
    </p>
    <noscript><img height=1 width=1 alt=""
    src="http://t0.extreme-dm.com/0.gif?tag=abc&j=n"></noscript>
    Elmbrook, Sep 28, 2003
    #1
    1. Advertising

  2. That's some dense shit, dude. But seriously I don't think you quoted all
    the relevent code to make heads or tails of this, looks like you only
    quoted the last line or two.

    These two statements:

    EXw?"":EXw="na";
    EXb?"":EXb="na";

    All they do is, if EXw and EXb are null, then set them to "na" (as in
    Not Available?). But it must be somewhere earlier in the code where they
    are setting EXw and EXb to initial values in the first place.

    In regards to the "j=y" statement; the way you've quoted the code, the
    variable j (and value y) are used entirely on the server. There is no
    client-side javascript here with a variable j and value of y. You need
    to look on the server side script (if you have it) to find out what the
    "j=y" is all about.

    Did you inherit this code from another developer, or are you trying to
    *ahem* learn from some other site's techniques?

    --

    Bryan Field-Elliot
    http://netmeme.org



    Elmbrook wrote:
    > Hi,
    >
    > I've been trying to figure out this javascript code used here (this code is
    > used for supplying browser info to a tracking company):
    >
    > In particular I'm trying to understand this line:
    > EXd=document;EXw?"":EXw="na";EXb?"":EXb="na";
    > and this one: EXd.write("<img
    > src=\"http://t0.extreme-dm.com","/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&
    > ","l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->
    >
    > Why do they have a variable j=y defined? There is no 'j' variable defined
    > in the code.
    >
    > If I modify the http://t0.extreme-dm.com and send the results to my ASP page
    > and use Querystrings to see what the values are, I only get the Screen width
    > and colour depth values. The referrer information is not showing. I also
    > don't understand how they can extract users country domain from this code.
    >
    > Thanks
    > Tristan
    > www.backpackpro.com
    >
    >
    > ----------- Complete code below ---------------
    >
    >
    > <a target="_top" href="http://t.extreme-dm.com/?login=abc"> <img
    > src="http://u1.extreme-dm.com/i.gif" height=2
    > border=0 width=2 alt=""></a>
    > <script language="javascript1.2"><!--
    > EXs=screen;EXw=EXs.width;navigator.appName!="Netscape"?
    > EXb=EXs.colorDepth:EXb=EXs.pixelDepth;//-->
    > </script>
    > <script language="javascript"><!--
    > EXd=document;EXw?"":EXw="na";EXb?"":EXb="na";
    > EXd.write("<img src=\"http://t0.extreme-dm.com",
    > "/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&",
    > "l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->
    > </script>
    > </p>
    > <noscript><img height=1 width=1 alt=""
    > src="http://t0.extreme-dm.com/0.gif?tag=abc&j=n"></noscript>
    >
    >
    Bryan Field-Elliot, Sep 28, 2003
    #2
    1. Advertising

  3. In article <C3Idb.4320$>,
    says...
    > Hi,
    >
    > I've been trying to figure out this javascript code used here (this code is
    > used for supplying browser info to a tracking company):
    >
    > In particular I'm trying to understand this line:
    > EXd=document;


    Set EXd to the "document" object;

    > EXw?"":EXw="na";


    If EXw is empty, set it to "na".

    > EXb?"":EXb="na";


    If EXb is empty, set it to "na".

    > and this one: EXd.write("<img
    > src=\"http://t0.extreme-dm.com","/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&
    > ","l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->


    That writes out an image using the values the script has just assigned.


    > Why do they have a variable j=y defined? There is no 'j' variable defined
    > in the code.


    The "j" isn't used in the code you've given here - it may be used in the
    server-side script that servers up the image, though. It's part of the
    URL, not part of the JavaScript. I imagine that other users may have
    "j" set to something else, otherwise there'd be no point having it.


    > If I modify the http://t0.extreme-dm.com and send the results to my ASP page
    > and use Querystrings to see what the values are, I only get the Screen width
    > and colour depth values.


    Perhaps your ASP that's trying to get the values is broken.


    > The referrer information is not showing. I also
    > don't understand how they can extract users country domain from this code.


    The won't extract the user's country domain from that code. They'll
    have their server-side code do it by tracking the remote IP address (ie.
    the site visitor's address) from which the request is made. It's rather
    inaccurate, though.

    --
    Hywel I do not eat quiche
    http://hyweljenkins.co.uk/
    http://hyweljenkins.co.uk/mfaq.php
    Hywel Jenkins, Sep 28, 2003
    #3
  4. Elmbrook

    Ivo Guest

    "Elmbrook" <> wrote in message
    news:C3Idb.4320$...
    > In particular I'm trying to understand this line:
    > EXd=document;EXw?"":EXw="na";EXb?"":EXb="na";


    EXw?"":EXw="na"
    is short for: if EXw has not been assigned a value in the preceding
    javascript1.2 block, give it a value of "na".

    > and this one: EXd.write("<img
    >

    src=\"http://t0.extreme-dm.com","/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&
    > ","l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->
    >
    > Why do they have a variable j=y defined? There is no 'j' variable defined
    > in the code.

    So what? Do you see tag, srw, srb anywhere else? This is where j gets
    defined. Think of y as a string of length 1. It probably means "javascript
    enabled=yes". Look in the noscript tag where you 'll find "j=n".
    Ivo, Sep 28, 2003
    #4
  5. Elmbrook

    Elmbrook Guest

    I'm trying to figure out how I can record the statistics of the visitors to
    my website, where they came from etc and send this to an ASP page.

    Are there Javascripts available for recording, referreal, domain etc?

    Thanks for your help


    "Bryan Field-Elliot" <> wrote in message
    news:IhIdb.455117$Oz4.260098@rwcrnsc54...
    > That's some dense shit, dude. But seriously I don't think you quoted all
    > the relevent code to make heads or tails of this, looks like you only
    > quoted the last line or two.
    >
    > These two statements:
    >
    > EXw?"":EXw="na";
    > EXb?"":EXb="na";
    >
    > All they do is, if EXw and EXb are null, then set them to "na" (as in
    > Not Available?). But it must be somewhere earlier in the code where they
    > are setting EXw and EXb to initial values in the first place.
    >
    > In regards to the "j=y" statement; the way you've quoted the code, the
    > variable j (and value y) are used entirely on the server. There is no
    > client-side javascript here with a variable j and value of y. You need
    > to look on the server side script (if you have it) to find out what the
    > "j=y" is all about.
    >
    > Did you inherit this code from another developer, or are you trying to
    > *ahem* learn from some other site's techniques?
    >
    > --
    >
    > Bryan Field-Elliot
    > http://netmeme.org
    >
    >
    >
    > Elmbrook wrote:
    > > Hi,
    > >
    > > I've been trying to figure out this javascript code used here (this code

    is
    > > used for supplying browser info to a tracking company):
    > >
    > > In particular I'm trying to understand this line:
    > > EXd=document;EXw?"":EXw="na";EXb?"":EXb="na";
    > > and this one: EXd.write("<img
    > >

    src=\"http://t0.extreme-dm.com","/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&
    > > ","l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->
    > >
    > > Why do they have a variable j=y defined? There is no 'j' variable

    defined
    > > in the code.
    > >
    > > If I modify the http://t0.extreme-dm.com and send the results to my ASP

    page
    > > and use Querystrings to see what the values are, I only get the Screen

    width
    > > and colour depth values. The referrer information is not showing. I

    also
    > > don't understand how they can extract users country domain from this

    code.
    > >
    > > Thanks
    > > Tristan
    > > www.backpackpro.com
    > >
    > >
    > > ----------- Complete code below ---------------
    > >
    > >
    > > <a target="_top" href="http://t.extreme-dm.com/?login=abc"> <img
    > > src="http://u1.extreme-dm.com/i.gif" height=2
    > > border=0 width=2 alt=""></a>
    > > <script language="javascript1.2"><!--
    > > EXs=screen;EXw=EXs.width;navigator.appName!="Netscape"?
    > > EXb=EXs.colorDepth:EXb=EXs.pixelDepth;//-->
    > > </script>
    > > <script language="javascript"><!--
    > > EXd=document;EXw?"":EXw="na";EXb?"":EXb="na";
    > > EXd.write("<img src=\"http://t0.extreme-dm.com",
    > > "/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&",
    > > "l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->
    > > </script>
    > > </p>
    > > <noscript><img height=1 width=1 alt=""
    > > src="http://t0.extreme-dm.com/0.gif?tag=abc&j=n"></noscript>
    > >
    > >

    >
    Elmbrook, Sep 28, 2003
    #5
  6. Spamless <> writes:

    > This uses
    >
    > A?B:C
    >
    > If A is true, then do B, otherwise do C.


    > If A is not a boolean test, but some variable,
    > then A? just checks if A is defined.


    That is not strictly correct.

    If A is an undeclared variable, then "A?B:C" fails with an "undeclared
    variable". If A is a declared variable, then its value is converted to
    a boolean (as by the Boolean function). The values that are converted
    to false are: 0, NaN, undefined, null, "" (empty string), and false
    itself.

    So, if A is defined but has the value 0, the "else" branch is still
    used.

    > EXw?"":EXw="na"


    personally, I would have written:

    EXw = EXw || "na";

    It has the same effect, is easier to read (IMHO), and is even shorter.

    What he really means is
    if(!EXw)EXw="na";
    but that is one charater longer.

    Where "if" is a statement that selects one of two *statements* based
    on a conditional expression, the ?:-operator is an expression that
    selects one of two expressions based on a condition. The original
    author uses it as a statement, which *I* think is bad style.

    /L
    --
    Lasse Reichstein Nielsen -
    Art D'HTML: <URL:http://www.infimum.dk/HTML/randomArtSplit.html>
    'Faith without judgement merely degrades the spirit divine.'
    Lasse Reichstein Nielsen, Sep 28, 2003
    #6
  7. All this stuff should be done server-side (e.g. ASP, JSP, Perl,
    whatever), rather than client-side (e.g. Javascript). From the server,
    you should have access to the referring URL and the IP address of the
    client (and from there, you can find their domoain). All this and more
    in the HTTP headers. No client-side Javascript required (or even useful).

    Better yet, your web server is probably already keeping this information
    in it's logs. Apache and IIS both support standard "Common" format for
    web hit logs, which includes client IP address and referring URL.

    Good luck,

    --

    Bryan Field-Elliot
    http://netmeme.org



    Elmbrook wrote:
    > I'm trying to figure out how I can record the statistics of the visitors to
    > my website, where they came from etc and send this to an ASP page.
    >
    > Are there Javascripts available for recording, referreal, domain etc?
    >
    > Thanks for your help
    >
    Bryan Field-Elliot, Sep 28, 2003
    #7
  8. Elmbrook

    Elmbrook Guest

    Thanks, but the problem is that some of my webpages are static and are being
    served by my local ISP. So when I found that this company had a way of
    sending stats to their server from my static page, I was interested in how
    they did it.



    "Elmbrook" <> wrote in message
    news:0bJdb.4329$...
    > I'm trying to figure out how I can record the statistics of the visitors

    to
    > my website, where they came from etc and send this to an ASP page.
    >
    > Are there Javascripts available for recording, referreal, domain etc?
    >
    > Thanks for your help
    >
    >
    > "Bryan Field-Elliot" <> wrote in message
    > news:IhIdb.455117$Oz4.260098@rwcrnsc54...
    > > That's some dense shit, dude. But seriously I don't think you quoted all
    > > the relevent code to make heads or tails of this, looks like you only
    > > quoted the last line or two.
    > >
    > > These two statements:
    > >
    > > EXw?"":EXw="na";
    > > EXb?"":EXb="na";
    > >
    > > All they do is, if EXw and EXb are null, then set them to "na" (as in
    > > Not Available?). But it must be somewhere earlier in the code where they
    > > are setting EXw and EXb to initial values in the first place.
    > >
    > > In regards to the "j=y" statement; the way you've quoted the code, the
    > > variable j (and value y) are used entirely on the server. There is no
    > > client-side javascript here with a variable j and value of y. You need
    > > to look on the server side script (if you have it) to find out what the
    > > "j=y" is all about.
    > >
    > > Did you inherit this code from another developer, or are you trying to
    > > *ahem* learn from some other site's techniques?
    > >
    > > --
    > >
    > > Bryan Field-Elliot
    > > http://netmeme.org
    > >
    > >
    > >
    > > Elmbrook wrote:
    > > > Hi,
    > > >
    > > > I've been trying to figure out this javascript code used here (this

    code
    > is
    > > > used for supplying browser info to a tracking company):
    > > >
    > > > In particular I'm trying to understand this line:
    > > > EXd=document;EXw?"":EXw="na";EXb?"":EXb="na";
    > > > and this one: EXd.write("<img
    > > >

    >

    src=\"http://t0.extreme-dm.com","/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&
    > > > ","l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->
    > > >
    > > > Why do they have a variable j=y defined? There is no 'j' variable

    > defined
    > > > in the code.
    > > >
    > > > If I modify the http://t0.extreme-dm.com and send the results to my

    ASP
    > page
    > > > and use Querystrings to see what the values are, I only get the Screen

    > width
    > > > and colour depth values. The referrer information is not showing. I

    > also
    > > > don't understand how they can extract users country domain from this

    > code.
    > > >
    > > > Thanks
    > > > Tristan
    > > > www.backpackpro.com
    > > >
    > > >
    > > > ----------- Complete code below ---------------
    > > >
    > > >
    > > > <a target="_top" href="http://t.extreme-dm.com/?login=abc"> <img
    > > > src="http://u1.extreme-dm.com/i.gif" height=2
    > > > border=0 width=2 alt=""></a>
    > > > <script language="javascript1.2"><!--
    > > > EXs=screen;EXw=EXs.width;navigator.appName!="Netscape"?
    > > > EXb=EXs.colorDepth:EXb=EXs.pixelDepth;//-->
    > > > </script>
    > > > <script language="javascript"><!--
    > > > EXd=document;EXw?"":EXw="na";EXb?"":EXb="na";
    > > > EXd.write("<img src=\"http://t0.extreme-dm.com",
    > > > "/0.gif?tag=abc&j=y&srw="+EXw+"&srb="+EXb+"&",
    > > > "l="+escape(EXd.referrer)+"\" height=1 width=1>");//-->
    > > > </script>
    > > > </p>
    > > > <noscript><img height=1 width=1 alt=""
    > > > src="http://t0.extreme-dm.com/0.gif?tag=abc&j=n"></noscript>
    > > >
    > > >

    > >

    >
    >
    Elmbrook, Sep 29, 2003
    #8
    1. Advertising

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