http://stackoverflow.com/questions/41991496/knockout-sortable-how-to-know-that-the-sortable-list-was-updated

knockout-sortable - simple list

HTML

<script src="http://knockoutjs.com/downloads/knockout-3.2.0.js"></script>
<script src="https://rawgithub.com/rniemeyer/knockout-sortable/master/build/knockout-sortable.js"></script>
<div class="container" data-bind="sortable: tasks">
  <div class="item">
    <a href="#" data-bind="text: name"></a>
  </div>
</div>


<div id="results">
  <ul data-bind="foreach: tasks">
    <li data-bind="text: name"></li>
  </ul>
</div>
<span style="color: red" data-bind="if: isUpdated">The list was updated!</span>

CSS

div {
  padding: 5px;
  margin: 5px;
  border: black 1px solid;
}

ul {
  padding-bottom: 10px;
}

.container {
  float: left;
  width: 150px;
  background-color: #ffd;
}

.item {
  background-color: #DDD;
  cursor: move;
  text-align: center;
}

#results {
  float: left;
  width: 150px;
}

JavaScript

var Task = function(name) {
  this.name = ko.observable(name);
}

var ViewModel = function() {
  var self = this;
  
  self.tasks = ko.observableArray([
    new Task("Get dog food"),
    new Task("Fix car"),
    new Task("Fix fence"),
    new Task("Walk dog"),
    new Task("Read book"),
     new Task("Read")
  ]);
  
  self.isUpdated = ko.observable(false);
  self.tasks.subscribe(function(value){
  	self.isUpdated(true);
  })
};

ko.applyBindings(new ViewModel());