<h1>Animate Callback Once width jQuery</h1>
<p>I have not failed. I’ve just found 10,000 ways that won’t work.(Thomas A. Edison)</p>
<p>When we go into that new project, we believe in it all the way. We have confidence in our ability to do it right. And we work hard to do the best possible job.(Walt Disney)</p>
<p>Liberty means responsibilty. That is why most men dread it.(George Bernard Shaw)</p>
<p>He who is to be a good ruler must have first been ruled.(Aristotle)</p>
<p>I am a great believer in luck and the harder I work the more I have of it.(Stephen Leacock)</p>
<p>Good leaders must first become good servants.(Robert K. Greenleaf)</p>
<p>The only man who never makes mistakes is the man who never does anything.(Theodore Roosevelt)</p>
<p>The quality of a leader is reflected in the standards they set for themselves.(Ray Kroc)</p>


<p class="button"><a class="callback_twice" href="#">callback twice</a></p>

<p class="button"><a class="callback_once" href="#">callback once</a></p>

* {
  text-align: center;
}

body {
  font-size: 16px;
  line-height: 200%;
}

.button a{
  margin-top:1rem;
  color: #555;
  background-color: #f5f5f5;
  text-decoration: none;
  position: relative;
  padding: 0.5em 0.5em;
  display: block;
  width: 35%;
  margin: 0px auto;
  background-image: -o-linear-gradient(bottom, rgb(206, 206, 206) 0%, rgb(252, 252, 252) 100%);
  background-image: -moz-linear-gradient(bottom, rgb(206, 206, 206) 0%, rgb(252, 252, 252) 100%);
  background-image: -webkit-linear-gradient(bottom, rgb(206, 206, 206) 0%, rgb(252, 252, 252) 100%);
  background-image: -ms-linear-gradient(bottom, rgb(206, 206, 206) 0%, rgb(252, 252, 252) 100%);
  background-image: -webkit-gradient( linear, left bottom, left top, color-stop(0, rgb(206, 206, 206)), color-stop(1, rgb(252, 252, 252)));
  -webkit-border-radius: 5px;
  -moz-border-radius: 5px;
  -o-border-radius: 5px;
  border-radius: 5px;
  -webkit-box-shadow: inset 0px 1px 0px #EBEBEB, 0px 5px 0px 0px #A8A8A8, 0px 7px 2px #999;
  -moz-box-shadow: inset 0px 1px 0px #EBEBEB, 0px 5px 0px 0px #A8A8A8, 0px 7px 2px #999;
  -o-box-shadow: inset 0px 1px 0px #EBEBEB, 0px 5px 0px 0px #A8A8A8, 0px 7px 2px #999;
  box-shadow: inset 0px 1px 0px #EBEBEB, 0px 5px 0px 0px #A8A8A8, 0px 7px 2px #999;
}

var callback = function() { console.log('done'); };

$('.callback_once').click(function() {
  var flag = false;
  $('html,body').animate({
    'scrollTop': 0
  }, 300, function() {
    if (flag) {
      flag = false;
      callback();
    } else {
      flag = true;
    }
  });
  return false;
});

var callback = function() {
  console.log('done');
};
$('.callback_twice').click(function() {
  $('html,body').animate({
    'scrollTop': 0
  }, 300, callback);
  return false;
});