jQuery .add method

I'm writing a simple jQuery plugin that displays images with a specific class in the center of the screen (when clicked, full-sized) with a gray overlay around the image. When we click on the overlay it disappears. Now I use this piece of code:

$("#overlay").click(function(){
        $(this).animate({
            opacity: "0"
        }, 500, function(){
            $(this).css({
                display: "none"
            });
        });

        $("#imgcontainer").animate({
            opacity: "0"
        }, 500, function(){
            $(this).css({
                display: "none"
            });

        });

    });

imgcontainer holds our image. I was trying to use this easier code, but it doesn't work:

$("#overlay").click(function(){
        $(this).add("#imgcontainer").animate({
            opacity: "0"
        }, 500, function(){
            $(this).css({
                display: "none"
            });
        });
    });

Why it doesn't work?

UPDATE:

Correct code:

$("#overlay").click(function(){
 开发者_StackOverflow中文版       $("#imgcontainer").add(this).fadeOut();
    });

Thanks a lot for replies. This behavior (bug?) is very surprising indeed.

If you're using v1.4.x, because of issue #7853 I just raised in their bug tracker earlier today (what timing!). You can fix it by changing this:

$(this).add("#imgcontainer").animate(...

to

$(this).add($("#imgcontainer")).animate(...

Update: Here's a better (more efficient) way, as Nick pointed out below:

$("#imgcontainer").add(this).animate(...

(See also his note about fadeOut.)

In jQuery 1.3.2 and earlier, it would have worked as you expected. I don't know whether the 1.4.x thing is a bug or an intentional incompatible change.

Question though: Why not just fade out the container? If it contains the image, that should fade the image too, shouldn't it? As in this example? (I don't do a lot of animation, so apologies if I've missed something subtle.) Never mind, you never said #overlay was the image, that was an invalid assumption on my part.