Trying to get this script to work on this site:

var t = $('#preschool-program').offset().top - 120;

        if($(this).scrollTop() > t) {   
        $('body.index header').css({"background-color":"rgba(0,0,0,1)"});

Scrolling down nearly 1/2way on the screen and the background header should turn opaque instead of staying semi-transparent. So I'm not sure why it's not working. Anyone?


There are several errors in your script and CSS, I'm not sure where to begin...

  • You're mixing $ and jQuery in your code. Joomla loads jQuery in noConflict mode, so you're better off using jQuery
  • The variable t cannot be set because it runs before the DOM is ready. Make sure you wait until the DOM is ready:

       var t = jQuery('#preschool-program').offset().top - 120; 
  • The second part should look like this:

        if(jQuery(this).scrollTop() > t) {   
            jQuery('body.index header').css({"background-color":"rgba(0,0,0,1)"});

    That basically works (the style is added to the header element), but the file http://nettra.net/demo-sites/wvg/development/templates/wvgs/css/bootstrap.css sets the background of the header using background: rgba(0,0,0,0.5)!important; at about line #10983, overriding your inline style. If you remove !important, and make the changes above, it should work.

  • 1
    so you're better off using jQuery >> You can also use $ as an alias which is good if you're used to using it >> jQuery(document).scroll(function($){ ;) – Lodder Sep 4 '15 at 1:31

Just an addition to @Johanpw's answer.

jQuery has some issues with the !important attribute when using .css() which you're going to have to use as Bootstrap is using it.

Here are 2 alternatives that you can use.

Solution 1:

You can apply your styling using the .style function:

$('body.index header').attr('style', 'background-color: rgba(0,0,0,1) !important');

Solution 2:

You could also add a class using jQuery and target this class using CSS which is much faster than applying the styling through jQuery itself.


$('body.index header').addClass('customBG');


.customBG {
    background-color: rgba(0,0,0,1) !important;

Full code using solution 1:

jQuery(document).ready(function ($) {
    var t = $('#preschool-program').offset().top - 120;
    $(document).scroll(function () {       
        if ($(this).scrollTop() > 0){ 
            $('body.index header').attr('style', 'background-color: red !important');
  • Isn't it the $ sign need to be replaced with 'jQuery' for better compatibility as @johanpw mentioned earlier ? – webchun Sep 4 '15 at 2:09
  • You see that I have used jQuery(document).ready(function($) {. This means jQuery is the global scope which is what @johanpw mentioned to prevent conflicts, but I have used $ as a local alias which will not cause conflicts as it's locked to only this scope – Lodder Sep 4 '15 at 10:17
  • Yeah, I managed to replace all of the '$' with jQuery, and that seemed to have fixed it. Plus, I had another version of jQuery running (DOH!). – user1813113 Sep 8 '15 at 19:58

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