jQuery 多个 animate() 回调

Question

I'm trying to animate a set of elements simultaneously (almost, there's a small delay between each animation):

$('.block').each(function(i){
   $(this).stop().delay(60 * i).animate({
     'opacity': 1
   }, {
      duration: 250,
      complete: mycallbackfunction // <- this fires the callback on each animation :(
   });
});

How can I run a callback function after all animations have completed?

Answer 1

Use a closure around a counter variable.

var $blocks = $('.block');
var count = $blocks.length;
$blocks.each(function(i){
   $(this).stop().delay(60 * i).animate({
     'opacity': 1
   }, {
      duration: 250,
      complete: function() {
        if (--count == 0) {
          // All animations are done here!
          mycallbackfunction();
        }
      }
   });
});

Note the saving of the list of items into the $block variable to save a lookup.

Answer 2

Since jQuery 1.5, you can use $.when ^[docs] , which is a bit easier to write and understand:

var $blocks = $('.block');

$blocks.each(function(i){
   $(this).stop().delay(60 * i).animate({
     'opacity': 1
   }, {
      duration: 250
   });
});

$.when($blocks).then(mycallbackfunction);

DEMO

Answer 3

Felix Kling's answer will fire the callback when there's no animation left to do. This makes the callback firing even if the animation is stopped via $el.stop() and thus not completed to the end.

I found an method by Elf Sternberg using deferred objects which I implemented in this jsfiddle:

http://jsfiddle.net/8v6nZ/

Answer 4

   var block = $('.block');
   block.each(function(i){
   $(this).stop().delay(60 * i).animate({
     'opacity': 1
    }, {
      duration: 250,
      complete: i== (block.length-1) ? myCallbackFunction : function(){}
    });
   });

Answer 5

$('.block').each(function(i){
   $(this).stop().delay(60 * i).animate({
     'opacity': 1
   }, {
      duration: 250,
      complete: ((i == $('.block').length - 1) ? mycallbackfunction : null)
   });
});