Moving between lists: ng-animate-ref

var app = angular.module('plunker', ['ngAnimate']);

app.controller('MainCtrl', function($scope) {
  $scope.listA = [{id:1}, {id:2}, {id:3}, {id:4}, {id:5}];
  $scope.listB = [{id:6}];
  
  $scope.moveToListB = function(item) {
    $scope.listB.push(item);
    $scope.listA.splice($scope.listA.indexOf(item), 1);
  };
  
  $scope.moveToListA = function(item) {
    $scope.listA.push(item);
    $scope.listB.splice($scope.listB.indexOf(item), 1);   
  };
});

<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link href='http://fonts.googleapis.com/css?family=Roboto' rel='stylesheet' type='text/css'>
    <link rel="stylesheet" href="style.css" />
    <script data-require="angular.js@1.4.x" src="https://code.angularjs.org/1.4.2/angular.js" data-semver="1.4.3"></script>
    <script data-require="angular.js@1.4.x" src="https://code.angularjs.org/1.4.2/angular-animate.js" data-semver="1.4.3"></script>
    <script src="app.js"></script>
  </head>

  <body ng-controller="MainCtrl">
    <div class="lists">
      <ul class="list" title="List A">
        <li class="item" ng-repeat="item in listA" ng-click="moveToListB(item)"><span class="item-contents" ng-animate-ref="{{ item.id }}">Item: {{ item.id }}</span></li>
      </ul>
      <ul class="list" title="List B">
        <li class="item" ng-repeat="item in listB" ng-click="moveToListA(item)"><span class="item-contents" ng-animate-ref="{{ item.id }}">Item: {{ item.id }}</span></li>
      </ul>
    </div>
  </body>

</html>

* {
  box-sizing: border-box;
}

body {
  font-family: Roboto, Helvetica, Arial;
  font-size: 12px;
}

.lists {
  display: flex;
  min-height: 150px;
}

.list:before {
  content: attr(title);
  background: #eeeeee;
  display: block;
  padding: 10px;
  font-weight: bold;
  margin-bottom: 10px;
}

.list {
  width: 200px;
  border: 1px solid #eeeeee;
  padding: 0 0 10px 0;
}

.list + .list {
  border-left: none;
}

.item {
  -webkit-touch-callout: none;
  -webkit-user-select: none;
  -khtml-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}

.item {
  cursor: pointer;
  display: block;
  margin: 0;
  padding: 0;
  width: 150px;
  height: 30px;
  overflow: hidden;
}

.item:hover {
  color: blue;
}

.item-contents {
  display: block;
  width: 200px;
  height: 30px;
  line-height: 30px;
  padding: 0 10px;
}

/* Contents are cloned and position transitioned between the lists */
.item-contents.ng-anchor-out {
  /* No "out" transition: the item moving accross the page is exactly how it
     appears in the source location */
}
.item-contents.ng-anchor-in {
  transition: 0.2s linear all;
}

/* The item height is transitioned so space appears/disappears gradually in each list */
.item.ng-enter {
  transition:0.1s linear all;
  height: 0;
}

.item.ng-enter.ng-enter-active {
  height: 30px;
}

.item.ng-leave {
  transition: 0.1s linear all;
  height: 30px;
}

.item.ng-leave.ng-leave-active {
  height: 0;
}