jQuery animation detect if animating?

Is their a way to detect 开发者_运维知识库if an element is animating or detect if values of an element is changing?

Because I need to trigger a function if an element is animating. Not onComplete of animate.

The following returns true when the selected element is animating:

var isAnimating = $("#someid").is(':animated');

More detail:

http://api.jquery.com/animated-selector/
and/or
http://api.jquery.com/animate/
step: A function to be called after each step of the animation.

A simple way would be adding a global boolean that gets set to true as soon as the animation starts. Then you add a callback function to the animation that sets it to false as it finishes.

var running = false;

$('#start').click(function(){

    running = true;

    $('#target').animate({opacity: 0.5},'slow',function(){

        running = false;

    });

});

Edit: Oh I guess there's a selector for it.