jQuery ajax, wait until beforeSend animation finishes

Question

HTML & CSS:

<a href="#">link</a>
<img src="http://2.bp.blogspot.com/_OIHTbzY7a8I/TOaiTKLqszI/AAAAAAAAAHM/eb3iiOqxzKg/s640/Auto_Audi_Audi_concept_car_005130_.jpg" />
<div></div>

img { display: none; }
a { display: block; }

JS:

$("a").click(function(){
    $.ajax({
        url: "test.php",
        contentType: "html",
        beforeSend: function(){
            $("img").fadeIn(600, function(){
                $("div").append(" | beforeSend finished | ");
            });
        },
        error: function(){
            $("div").append(" | error | ");
        }
    });
    return false
});

The problem is, error function starts, before animation in beforeSend function finishes.

Here is working example http://jsfiddle.net/H4Jtk/2/

error should begin to work only when beforeSend is finished. How to do this?

I use beforeSend function to start animation of the blocks when ajax starts. I can't remove it.

Thanks.

Answer 1

You can use a custom event to wait until the animation is complete, like this:

$("a").click(function(){
    var img = $("img"),
        div = $("div");
    $.ajax({
        url: "test.php",
        contentType: "html",
        beforeSend: function(){
            img.fadeIn(600, function(){
                div.append(" | beforeSend finished | ");
                div.trigger("animationComplete");
            });
        },
        error: function(){
            if(img.is(':animated')) {
                div.one("animationComplete", function() {
                    div.append(" | error | ");
                });
            } else {
                div.append(" | error | ");
            }
        }
    });
    return false
});

Notes:

1. jQuery.one() attaches an event handler that fires once and is then removed.
2. jQuery.is(':animated') is a custom selector provided by jQuery to determine if an element is animated using jQuery's built-in animation methods (eg fadeIn).

New jsFiddle: http://jsfiddle.net/pgjHx/

---

In the comments, Happy has asked how to handle multiple animations. One way would be to add a condition to the animationComplete event handler to see if animation is ongoing. For example:

$("a").click(function(){
    var img = $("img"),
        div = $("div");

    $.ajax({
        url: "test.php",
        contentType: "html",
        beforeSend: function(){
            img.fadeIn(600, function(){
                div.append(" | beforeSend finished | ");
                div.trigger("animationComplete");
            });

            // Add another animation just to demonstrate waiting for more than one animation
            img.animate({
                marginTop: '-=5',
                opacity: '-=.5'
            }, 700, function() {    
                div.trigger("animationComplete");
            });
        },
        error: function(){
            if(img.is(":animated")) {
                // Note I've switched to bind, because it shouldn't be unbound
                // until all animations complete
                div.bind("animationComplete", function() {
                    if(img.is(":animated")) {
                        return;
                    }
                    div.append(" | error | ");
                    div.unbind("animationComplete");
                });
            } else {
                div.append(" | error | ");
            }
        }
    });
    return false
});