[jquery] How to check if image exists with given url?

From here:

// when the DOM is ready
$(function () {
  var img = new Image();
  // wrap our new image in jQuery, then:
  $(img)
    // once the image has loaded, execute this code
    .load(function () {
      // set the image hidden by default    
      $(this).hide();
      // with the holding div #loader, apply:
      $('#loader')
        // remove the loading class (so no background spinner), 
        .removeClass('loading')
        // then insert our image
        .append(this);
      // fade our image in to create a nice effect
      $(this).fadeIn();
    })
    // if there was an error loading the image, react accordingly
    .error(function () {
      // notify the user that the image could not be loaded
    })
    // *finally*, set the src attribute of the new image to our image
    .attr('src', 'images/headshot.jpg');
});