Tuesday, March 09, 2010

jQuery's show() function does not work on my BlackBerry ... sometimes :-)

Sometimes the show function in jQuery does not work in the (4.6.1) BlackBerry browser. Below is a detailed explanation the problem, followed by a solution showing how to fix this, and then an educated guess at the reason for the problem:

1) The problem may occur if you have something like the following javascript code in your web page:
<script src="js/jquery-1.4.1.min.js" ></script>
$(document).ready( function() {
$('div.features').hide(); // hide all divs of class="features"
$('div.features').first().show(); // show the first div of class "features"
function reveal(featureId) {
$('div.features').hide(); // hide all divs of class="features"
$('div#' + featureId).show(); // show the div with id=featureId
<select onchange="reveal(this.options[selectedIndex].value)" >
<option value="feature1" >BB Browser feature 1</option>
<option value="feature2" >BB Browser feature 2</option>
<option value="feature3" >BB Browser feature 3</option>
<div id="feature1" class="features">BB Browser feature 1</div>
<div id="feature2" class="features">BB Browser feature 2</div>
<div id="feature3" class="features">BB Browser feature 3</div>
Now if the "reveal" function is called using the <select onchange="reveal(...)"> as shown above, the call to the show() function will sometimes not have the desired effect of changing the display style of the div from "none" to "block".

2) My suggested solution or fix for this:
Use .css("display", "block") instead of .show()

3) Why is this happening only on my BlackBerry?
It appears that on the BlackBerry browser (at least the version noted) there is a race condition that causes this as follows:
a) Sometimes jQuery's data cache of the display values is set before the $(document).ready function is called, and so the styles are all cached as "display:block" which results in the expected behavior.

b) but sometimes jQuery's data cache of the display values occurs after the $(document).ready function is called, and so the styles are cached as "display:none" (except for the first one in this example). Which results in only being able to "reveal" the first feature ... jQuery's show() function is in fact getting called in any case. It is simply setting the display style to the cached value which is "none" in this case.

c) It appears that this issue starts occurring only after returning to the page a few times, or by returning to the page using a bookmark. You can try it here with your BlackBerry browser.
There may be some magic jQuery function that could be called in $(document).ready function before the hide(s) take place to make sure that jQuery's data cache is populated with the desired values first, but I'll leave that and any other errors in this discription of the issue to the jQuery experts in the comments below :-)

Hope that helps.

NOTE: This was discovered while testing with a BlackBerry 8350i running v4.6.1.204 of the BlackBerry OS using the jQuery.fn.show function with javascript turned on, of course.
NOTE: This was discovered using jquery-1.4.1.min.js
NOTE: Could not reproduce this issue using a BlackBerry 9700 running v5.0.0.330 of the BlackBerry OS ... it just works fine.

Thursday, March 04, 2010

The good and the bad ...

How many trashy youtube videos get advertised for us to see? How many comments are made about each and every detail of those videos? Now let's examine the other edge of the sword of truth. How many good things can you find in a video like this ...