javascript - Wait until image loads before performing function

Question

I'm trying to create a simple portfolio page. I have a list of thumbs and an image. When you click on a thumb, the image will change.

When a thumbnail is clicked, I'd like to have the image fade out, wait until the image is loaded, then fade back in. The problem I have right now is that some of the images are pretty big, so it fades out, then fades back in immediately, sometimes while the image is still loading.

I'd like to avoid using setTimeout, since sometimes an image will load faster or slower than the time I set.

Here's my code:

 $(function() {
     $('img#image').attr("src", $('ul#thumbs li:first img').attr("src"));

     $('ul#thumbs li img').click(function() {
         $('img#image').fadeOut(700);

         var src = $(this).attr("src");
         $('img#image').attr("src", src);

         $('img#image').fadeIn(700);
     });
 });

<img id="image" src="" alt="" />
<ul id="thumbs">
    <li><img src="/images/thumb1.png" /></li>
    <li><img src="/images/thumb2.png" /></li>
    <li><img src="/images/thumb3.png" /></li>
</ul>

Answer 1

You can do it like this:

$('img#image').attr("src", src).one('load',function() {
  $(this).fadeIn(700);
}).each(function() {
  if (this.complete) $(this).trigger('load');
});

If an image is cached, in some browsers .load() won't fire, so we need to check for and handle this case by checking .complete and firing load manually. .one() ensures whether it's cached or loaded at that time, that the load handler only fires once.