Centering draggable elements inside droppable using jquery-ui

Question

Below is an example of what I have been able to achieve so far...

$(document).ready(function() {
  $(".item").draggable({
    revert: 'invalid',
    snapMode: 'inner',
    scroll: false,
    stack: false,
    drag: function(event, ui) {
      $(".droparea").removeClass("highlight");
    }
  });
  $(".droparea").droppable({
    tolerance: 'intersect',
    drop: function(event, ui) {
      var drop_el = $(this).offset();
      var drag_el = ui.draggable.offset();
      var left_end = (drop_el.left + ($(this).width() / 2)) - (drag_el.left + (ui.draggable.width() / 2));
      var top_end = (drop_el.top + ($(this).height() / 2)) - (drag_el.top + (ui.draggable.height() / 2));
      $(this).addClass("highlight").find("p");
      ui.draggable.animate({
        top: '+=' + top_end,
        left: '+=' + left_end
      });
    }
  });
});

.item {
  position: relative;
  margin: 0 auto;
  width: 100px;
  height: 100px;
  border: 1px solid red;
  margin-top: 50%;
  top: -50px
}
.droparea {
  width: 150px;
  height: 150px;
  float: left;
  margin: 10px;
  border: 1px solid #000;
}
.highlight {
  border: 1px solid blue
}

<script src="http://code.jquery.com/jquery-1.11.1.min.js"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.10.4/jquery-ui.js"></script>

<div class="droparea">
  <div class="item"></div>
</div>

<div class="droparea">

</div>

Sometimes it refuses to center the .item div... The .item div has to be dragged into the inner part of the .droparea element, otherwise it won't center the .item element after releasing the item element. Just wondering if there is any more elegant way to make a draggable div centered into the closest droppable element.

Answer 1

You can use jQuery UI's inbuilt position() utility method for centering the dropped item as follows:

$(document).ready(function() {
  $(".item").draggable({
    scroll: false,
    revert: 'invalid',
    stack: false,
    cursor: "pointer",
    drag: function(event, ui) {
      $(".droparea").removeClass("highlight");
    }
  });
  $(".droparea").droppable({
    accept: ".item",
    drop: function(event, ui) {
      var $this = $(this);
      $(".highlight").removeClass("highlight");
      $this.addClass("highlight");
      ui.draggable.position({
        my: "center",
        at: "center",
        of: $this,
        using: function(pos) {
          $(this).animate(pos, "slow", "linear");
        }
      });
    }
  });
});

.item {
  position: relative;
  margin: 0 auto;
  width: 100px;
  height: 100px;
  border: 1px solid red;
}
.droparea {
  width: 150px;
  height: 150px;
  float: left;
  margin: 2px;
  border: 1px solid #000;
  outline: 1px solid transparent
}
.highlight {
  border: 1px solid blue
}

<script src="http://code.jquery.com/jquery-1.11.1.min.js"></script>
<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.10.4/jquery-ui.js"></script>

<div class="droparea">
  <div class="item"></div>
</div>


<div class="droparea"></div>
<div class="droparea"></div>