jQuery Looping Animation pauses each time. How to keep from pausing?_问答_开发者

I am trying to cause a block to "pulsate" between 100% opacity and some partially transparent opacity. I want to do this with the functionality that is built into the jQuery core, if possible. I would rather not add a plugin to get this effect. Here is the code that i am trying to use:

    $(document).ready(function() {
 function pulsate() {
  $("#pulsating-block").animate({opacity: 0.2}, 3000).animate({opacity: 1}, 3000, null, function() {pulsate()});
 }
 pulsate();  });

The problem is that each time the animation completes, it pauses for about a second before looping again. How can I keep it from pausing so that I get a smooth "pulsating" ef开发者_C百科fect? (Note: the animation is exaggerated in this example to highlight the problem that I am having)

Perhaps your issue is with the "swing" easing function jQuery uses by default.

You might want to try the "linear" easing function instead:

$(document).ready(function() {
  function pulsate() {
    $("#pulsating-block").
      animate({opacity: 0.2}, 3000, 'linear').
      animate({opacity: 1}, 3000, 'linear', pulsate);
  }
  pulsate();
});

I've also coded up a small pulsate plugin that includes a "bounce" easing function that may be more to your liking. I should note that the plugin uses a continuous calculation to perform the animation, not two separate fade-in/fade-out animations, so it might help with the "pause" issue. (To be honest, I still don't see the pause you are talking about.)

Working Demo

http://jsbin.com/isicu (editable via http://jsbin.com/isicu/edit)

Full Source

JavaScript

(function ($) {
  $.fn.pulsate = function (properties, duration, type, speed, callback) {
    type = type || 'Swing'
    speed = speed || 'Normal';
    this.animate(properties, duration, 'pulsate' + type + speed, callback);
  };

  function createPulsateLinear (speed) {
    speed *= 2;
    return function (p, n) {
      return (Math.asin(Math.sin(Math.PI * n / speed)) + Math.PI / 2) / Math.PI;
    }
  }

  function createPulsateSwing (speed) {
    return function (p, n) {
      return (1 + Math.sin(n / speed)) / 2;
    }
  }

  function createPulsateBounce (speed) {
    speed *= 2;
    return function (p, n) {
      return (
        ((Math.asin(Math.sin(Math.PI * n / speed)) + Math.PI / 2) / Math.PI) *
        (Math.sin(Math.PI * n / speed) + 1) / -2 + 1
      );
    }
  }

  var speeds = {
    fast: 100,
    normal: 200,
    slow: 400
  }

  $.extend(jQuery.easing, {
    pulsateLinearFast: createPulsateLinear(speeds.fast),
    pulsateLinearNormal: createPulsateLinear(speeds.normal),
    pulsateLinearSlow: createPulsateLinear(speeds.slow),
    pulsateSwingFast: createPulsateSwing(speeds.fast),
    pulsateSwingNormal: createPulsateSwing(speeds.normal),
    pulsateSwingSlow: createPulsateSwing(speeds.slow),
    pulsateBounceFast: createPulsateBounce(speeds.fast),
    pulsateBounceNormal: createPulsateBounce(speeds.normal),
    pulsateBounceSlow: createPulsateBounce(speeds.slow)
  });
})(jQuery);

$(document).ready(function() {
  var
    pulsatingBlocks = $('.pulsating-block'),
    forever = 5 * 24 * 60 * 60 * 1000; // 5 days! (Which is forever in Internet time)

  pulsatingBlocks.filter('.opacity').each(function () {
    $(this).pulsate({opacity: 0.2}, forever, this.className.split(' ')[0], 'Slow');
  });

  pulsatingBlocks.filter('.top').each(function () {
    $(this).pulsate({top: 100}, forever, this.className.split(' ')[0], 'Slow');
  });

});

HTML

<!DOCTYPE html>
<html>
<head>
<script class="jsbin" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.js"></script>
<meta charset=utf-8 />
<title>Pulsate</title>
<style>
  div { clear: left; margin-bottom: 2em; }
  .pulsating-block {
    width: 6em; height: 4em;
    margin: 0.5em; margin-right: 10em;
    float: left; clear: none; position: relative;
    background: lightblue;
    text-align: center;
    padding-top: 2em;
    font: bold 1em sans-serif;
  }
</style>
</head>
<body>
  <div>
    <div class="Linear opacity pulsating-block">linear</div>
    <div class="Swing opacity pulsating-block">swing</div>
    <div class="Bounce opacity pulsating-block">bounce</div>
  </div>
  <div>
    <div class="Linear top pulsating-block"></div>
    <div class="Swing top pulsating-block"></div>
    <div class="Bounce top pulsating-block"></div>
  </div>
</body>
</html>

try

 function pulsate() {
      $("#pulsating-block").animate({opacity: 0.2}, 3000,function(){
          $(this).animate({opacity: 1}, 3000, null, function() {pulsate()});
      });
     }