Volodymyr's blog: 2009

I am the one who uses package managers to install/update software and believes that is actually a good way. There are some people who don't use them at all and relay on manual installation only using make, make install. Well, this approach works perfectly until software doesn't have a lot of dependencies which are difficult to carry out manually.. That happened to me when I tried manually to install dsniff under Debian. The command apt-cache search dsniff didn't find the required package and therefore I downloaded sources and tried to install them manually. No success, coz there were required many other libraries to be installed which on the other hand couldn't not be installed due to conflicts with already installed software..

Since I am a newbie to debian I didn't know that there are stable and unstable branches in the package manager and so didn't find dsniff under stable branch. Here is a way how to install dsniff:

first update your package list with unstable software:

apt-get -t unstable update

then install the package:

apt-get install dsniff

Recently on the project I am working on we had a problem regarding changing stylesheets. There was a big tree and we needed to have as fast as possible way of changing styles of all nodes in the tree. One solution is to construct a jquery selector, iterate through all the nodes and change styles respectively. It is a nice approach at the first hand but it turns out to be an inefficient one. For this reason we decided to change global styles, thereby not spending running time on js loops.

I measured performance for different approaches. Below are results.
First I generated a page with 10 thousand div tags on it:

<html>
<head>
  <script type="text/javascript" src="scripts/jquery.js"></script>
  <script type="text/javascript" src="http://flesler-plugins.googlecode.com/files/jquery.rule-1.0.1.js"></script>
  <script type="text/javascript" src="http://remysharp.com/time.js"></script>

  <script type="text/javascript">
    function changeStyles1() {
      time.start("changeStyles1");
      $("div.dv").css("background-color", "Silver");
      $("a.lnk").css("color", "Black");
      time.stop("changeStyles1");
      time.report();
    }
    function changeStyles2() {
      time.start("changeStyles2");
      var html = "<style type='text/css'>.dv{background-color: Silver;} .lnk{color: Black;}</style>";
      $("div#styles").html(html);
      time.stop("changeStyles2");
      time.report();
    }
    function changeStyles3() {
      time.start("changeStyles3");
      var html = "<style type='text/css'>.dv{background-color: Silver;} .lnk{color: Black;}</style>";
      $("div#styles").html(html);
      time.stop("changeStyles3");
      time.report();
    }
  </script>

</head>
<body>
  <div id="styles">
    <style type="text/css">
      .dv
      {
        background-color: Yellow;
      }
      .lnk
      {
        color: Red;
      }
    </style>
  </div>

  Change styles using:
  <button onclick="changeStyles1();">
    jquery selectors</button>
  <button onclick="changeStyles2();">
    global styles</button>
  <button onclick="changeStyles3();">
    jQuery.rule</button>

  <div id="container">
    <div class='dv'>div # 0 <br/><a href='about:blank' class='lnk'>Link # 0</a></div>
    <div class='dv'>div # 1 <br/><a href='about:blank' class='lnk'>Link # 1</a></div>
    <div class='dv'>div # 2 <br/><a href='about:blank' class='lnk'>Link # 2</a></div>
    <div class='dv'>div # 3 <br/><a href='about:blank' class='lnk'>Link # 3</a></div>
    <div class='dv'>div # 4 <br/><a href='about:blank' class='lnk'>Link # 4</a></div>
    <div class='dv'>div # 5 <br/><a href='about:blank' class='lnk'>Link # 5</a></div>
...

  </div>
</body>
</html>

Example:

Change styles using:

div # 0
Link # 0

div # 1
Link # 1

div # 2
Link # 2

div # 3
Link # 3

div # 4
Link # 4

div # 5
Link # 5

Then I tested running time in IE7 and Mozilla 3.5:

	jQuery selectors	global styles	jQuery.rule
IE7	2834 ms	15 ms	17 ms
Mozilla	1108 ms	10 ms	6 ms

Personally I prefer "global styles" approach cause in case when one has to change many styles at once it works faster than other methods and forces browser to update its stylesheet collection only once.
Used libraries:

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Sunday, November 8, 2009

Installing dsniff on debian

Thursday, October 15, 2009

Switching styles dynamically

Monday, October 12, 2009

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