Preloading images with jQuery

preloader.js

/**
 * Preloads the image, and invokes the callback as soon 
 * as the image is loaded.
 */
var preload = function(src, callback) {
  // Create a temporary image.
  var img = new Image();

  // Invoke the callback as soon as the image is loaded
  // Has to be set **before** the .src attribute. Otherwise
  // `onload` could fire before the handler is set.
  $(img).load(callback);

  img.src = src;
};


// Example usage:

var $body = $(body);
$body.addClass("loading-background");
var backgroundImage = "/imag/background.jpg";

preload(backgroundImage, function() {
  $(body).removeClass("loading-background");
  $body.css({ backgroundImage: "url(" + backgroundImage + ")" });
});