How can I check if a background image is loaded?

Question

I want to set a background image on the body tag, then run some code - like this:

$(\'body\').css(\'background-image\',\'http://picture.de/image.png\').load(         


        

Answer 1

Here is a simple vanilla hack ~

(function(image){
  image.onload = function(){ 
                   $(body).addClass('loaded-background');
                   alert('Background image done loading');
                   // TODO fancy fade-in
                 };
  image.src    = "http://picture.de/image.png";
})(new Image());

Answer 2

There are no JS callbacks for CSS assets.

Answer 3

Something like this:

var $div = $('div'),
  bg = $div.css('background-image');
  if (bg) {
    var src = bg.replace(/(^url\()|(\)$|[\"\'])/g, ''),
      $img = $('<img>').attr('src', src).on('load', function() {
        // do something, maybe:
        $div.fadeIn();
      });
  }
});

Answer 4

Here is a small plugin I made to allow you to do exactly this, it also works on multiple background images and multiple elements:

Read the article:

http://catmull.uk/code-lab/background-image-loaded/

or go straight to the plugin code:

http://catmull.uk/downloads/bg-loaded/bg-loaded.js

So just include the plugin and then call it on the element:

<script type="text/javascript" src="http://catmull.uk/downloads/bg-loaded/bg-loaded.js"></script>
<script type="text/javascript">
   $('body').bgLoaded();
</script>

Obviously download the plugin and store it on your own hosting.

By default it adds an additional "bg-loaded" class to each matched element once the background is loaded but you can easily change that by passing it a different function like this:

<script type="text/javascript" src="http://catmull.uk/downloads/bg-loaded/bg-loaded.js"></script>
<script type="text/javascript">
   $('body').bgLoaded({
      afterLoaded : function() {
         alert('Background image done loading');
      }
   });
</script>

Here is a codepen demonstrating it working.

http://codepen.io/catmull/pen/Lfcpb