<!DOCTYPE html>
<html>

  <head>
    <script data-require="angular.js@1.4.1" data-semver="1.4.1" src="https://code.angularjs.org/1.4.1/angular.js"></script>
    <link rel="stylesheet" href="style.css" />
    <script src="script.js"></script>
  </head>

  <body ng-app="app1" ng-controller="foo">
    <select ng-model="sample" 
        ng-options="item.text for item in list track by item.key">
    </select>
    <p>{{sample | json}}</p>
  </body>

</html>
// Code goes here

angular.module("app1", []).controller("foo", function($scope) {
  $scope.list = [
      {key: "1", text: "One"},
      {key: {id:2}, text: "Two"},
      {key: {id:3}, text: "Three"}
    ];
});

angular.bootstrap(body, "app1");
/* Styles go here */

AngularJS 1.4: select track by