Adding and using jQuery on Blogger / Blogspot

Investigating my visitors statistics, I noticed that there were some users who were interested in adding and using jQuery on their Blogger.com (Blogspot.com) accounts. Adding jQuery library to your Blogger/Blogspot blog is not difficult. All you have to do is to add one line of code to your template’s header.

Here is the code to add to your blogger template’s header:

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6
/jquery.min.js" type="text/javascript"></script>

NOTE:

You don’t even need to upload jquery.js file on any other hosting Google will host it for your.

Instruction for adding jQuery to Blogger:

Login to your dashboard;
Choose your blog;
From the top menu select “Layout”;
Then select “Edit HTML” sub-menu;
Add the above code just below tag (or alternatively, just above tag)

If you have better solution, just tell me !

jQuery AJAX functions (load(), $.get(), etc.) are not loading new page versions problem

Today I would like to share with you a quick solution to the common problem when your AJAX calls to some page that changes over time is not being loaded to your page. In other words, jQuery or your browser is not loading new version of the page.

This problem is common in Mozilla Firefox (FF). Internet Explorer (IE) users I believe, do not experience this problem. Usually it occurs when you use jQuery AJAX functions in javascript setInterval() method. Basically, what happens is that Firefox can not see the changes been made to the page and thinks it’s the same with the old one. So Firefox loads it from cache and you don’t see the new version of your page. To resolve this issue, you should simply add a random string to the request like below.

The solution:

// Reload mypage.html every 5 seconds
var refresh = setInterval(function()
{
    // Minimized code, suggested by Kovacs
    $('#mydiv').load("mypage.htm?" + 1*new Date() );

}, 5000);

If you have better solution, just tell me !

Problems with jQuery mouseover / mouseout events

Today I have a quick note for you that will probably save you time someday. Basically it’s a workaround for a bug when you have parent element with children elements and parent element has mouseover or mouseout event. Moving your mouse over children elements may fire mouseout event of their parent. This is caused by event bubbling / propagation and if you would like to have a quick solution just read the solution at the bottom of this post. If you would like to understand it in more details please search Google for event propagation.

The problem:
When you have mouseover and mouseout events bound to some element on you page with children elements. Hovering over children element fires parent’s mouseover and/or mouseout event.

The solution:
The solution to this error is to use mouseenter and mouseleave events instead of mouseover and mouseout.

The reason:
This solution works because mouseover and mouseout events do not bubble from child to parent element.

Javascript for() loop vs jQuery .each() performance comparison

This post is an outcome of 15 minutes of free time and a question that I had yesterday. This question were:

How fast jQuery’s .each() method is?
How does it compare to javascript’s native for loop?
It is clear without any performance tests that native javascript for loop is faster, but I always used jQuery’s .each() utility with caution. It always felt like I will get a performance penalty for using it. So I tried to never use it.

So today, I wrote up a little javascript performance test and got my answers. Basically, I created an array and iterated through it using native for loop and jQuery’s .each() iterator. All I did was just an iteration and no array amendments or any other logic. I know it is very basic, but that’s exactly what I want to know. How fast they iterate!

Performance test code:

console.time('TestNative');
for( i=0; i < myArray.length; i++){
  myArray[i];
}
console.timeEnd('TestNative');

console.time('TestjQuery');
jQuery.each(myArray, function(i, val) {
  val;
});
console.timeEnd('TestjQuery');

Performance test results:

JavaScript Native FOR loop

Array size     Time
==========    ======
10,000        7ms
100,000       62ms
1,000,000     613ms


jQuery .each() loop

Array size     Time
==========    ======
10,000        10ms
100,000       177ms
1,000,000     1100ms

Usually we don’t have more than 1000 items in our arrays and objects, that is why I guess it can be concluded that using .each() loop in our code will not cause any performance penalties.

Dynamically adding table row count number using JavaScript and jQuery

Recently on jQuery mailing list a user asked how he/she could add a row count in their table automatically. So I wrote a code snippet which looks like this:

$(document).ready(function(){
  $("table").each(function(){
    if($(this).is('table')){
      $('thead th:first-child, thead td:first-child', this).each(
                                                   function(){
        if($(this).is('td'))
          $(this).before('<td>#</td>');
        else if($(this).is('th'))
          $(this).before('<th>#</th>');
      });
      $('tbody td:first-child', this).each(function(i){
        $(this).before('<td>'+(i+1)+'</td>');
      });
    }
  });
});

This code was for specific case, where there is only one table on the page and it has only one row in its header. That is why I took into the account the possibility of row spans and multi line rows in header and rewrote the code. Then made a plugin out of it. So, here is the final code:

function($){ $.fn.extend({ addCount: function() { return $(this).each(function(){ if($(this).is('table')){ $('thead th:first, thead td:first', this).each(function(){ if($(this).is('td')) $(this).before('<td rowspan="'+$('thead tr').length+'">#</td>'); else if($(this).is('th')) $(this).before('<th rowspan="'+$('thead tr').length+'">#</th>'); }); $('tbody td:first-child', this).each(function(i){ $(this).before('<td>'+(i+1)+'</td>'); }); } }); } }); })(jQuery);

To apply it to your tables use this code:

$('table').addCount();
$('.some-table-class').addCount();
$('#some-table-id').addCount();

If you have better solution, just tell me !

QR Code (generator) plugin for jQuery & JavaScript

I recently came across a 2 dimensional barcode called QR Code. QR code’s are popular in Japan and they are mainly used there to quickly get to some website on their mobiles by simply taking a picture of the QR code. You may read more about QR codes on Wikipedia.

Here is an example of QR code for jQuery HowTo blog:

If you have a QR code reader on your mobile take a picture of it and it will open this website. Cool ha?!

Anyway, there are plenty of free online QR code generator sites, but no JavaScript and jQuery plugins/functions. So, I quickly searched for a free online QR code generator sites with “friendly” URL’s and put together a javascript and jQuery functions that generate QR barcode image’s URL for passed URLs. I used Kaywa & University of Bath services.

Here are javascript and jQuery QR code functions:

// JavaScript function
function qrcode(url, size){
  if(typeof(size) == 'undefined') size = 8;
  return 'http://qrcode.kaywa.com/img.php?s='+size+'&d='+url;
}
qrcode('http://jquery-howto.blogspot.com');

// jQuery plugin
(function ($) {
  $.fn.qrcode = function(url, size) {
    if(typeof(size) == 'undefined') size = 8;
    return 'http://qrcode.kaywa.com/img.php?s='+size+'&d='+url;
  }
})(jQuery);
$().qrcode('http://www.google.com');

The code above utilizes Kaywa’s online QR code generator. You can specify image site as the second argument to the function. The size argument mut be between 1 and 40 and the generated image will 32 x your argument.

Here is javascript and jQuery code for University of Bath barcode generator:

// JavaScript function
function qrcode(url){
  return 'http://go.bath.ac.uk/qr/download?DATA='+url;
}
qrcode('http://jquery-howto.blogspot.com');

// jQuery plugin
(function ($) {
  $.fn.qrcode = function(url) {
    return 'http://go.bath.ac.uk/qr/download?DATA='+url;
  }
})(jQuery);
$().qrcode('http://www.google.com');

If you have better solution, just tell me !

Cross domain AJAX querying with jQuery

This post IS NOT about jQuery’s JSONP support. This post is about how to make AJAX queries to domains other then yours. Basically how to achieve cross domain scripting with jQuery. The technique will help you resolve the access to restricted uri denied" code: "1012 problem.

Using this method for cross site scripting you will be able to:
Make AJAX queries to any domain even those that differ from your own;
Use any of $.get(), $.post(), $.ajax(), $getScript(), etc. jQuery AJAX functions as your query method.

But all these does not come free, you will need to put a proxy to between you and the rest of the world. This cross domain querying solution works because you actually loading the content from your own domain. You request the URL and the proxy script on your server actually loading the content from the internet and passing it over to you.
I created a sample PHP proxy that I used to get related news RSS feed for one of my projects.

The PHP script to use as a cross domain scripting proxy:

<?php
// Set your return content type
header('Content-type: application/xml');

// Website url to open
$daurl = 'http://feeds.feedburner.com/jQueryHowto';

// Get that website's content
$handle = fopen($daurl, "r");

// If there is something, read and return
if ($handle) {
    while (!feof($handle)) {
        $buffer = fgets($handle, 4096);
        echo $buffer;
    }
    fclose($handle);
}
?>

I named the file proxy.php and made my AJAX request to this url. Here is a jQuery code example:

$("#rssFeeds").load("path/to/proxy.php", function(){
  // Some callback functions
});

And this is how I overcame the jQuery cross site scripting problems. The bad news is that not all web hosting companies allow fopen() to other domains, but enable it on request. My web server was very strict on security but the script above worked well on it.

If you have better solution, just tell me !