angular.forEach();

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

function TodoCtrl($scope) {
  $scope.todos = [
    {text:'learn angular', done:true},
    {text:'build an angular app', done:false}];

  $scope.addTodo = function() {
    $scope.todos.push({text:$scope.todoText, done:false});
    $scope.todoText = '';
  };

  $scope.remaining = function() {
    var count = 0;
    angular.forEach($scope.todos, function(todo) {
      count += todo.done ? 0 : 1;
    });
    return count;
  };

  $scope.archive = function() {
    var oldTodos = $scope.todos;
    $scope.todos = [];
    angular.forEach(oldTodos, function(todo) {
      if (!todo.done) $scope.todos.push(todo);
    });
  };
}

<!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="style.css" rel="stylesheet" />
    <script data-semver="1.2.16" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.16/angular.min.js" data-require="angular.js@1.2.x"></script>
    <script src="app.js"></script>
  </head>

  <body>
  
 <div ng-app>
  <h2>Todo</h2>
  <div ng-controller="TodoCtrl">
    <span>{{remaining()}} of {{todos.length}} remaining</span>
    [ <a href="" ng-click="archive()">archive</a> ]
    <ul class="unstyled">
      <li ng-repeat="todo in todos">
        <input type="checkbox" ng-model="todo.done">
        <span class="done-{{todo.done}}">{{todo.text}}</span>
      </li>
    </ul>
    <form ng-submit="addTodo()">
      <input type="text" ng-model="todoText"  size="30"
             placeholder="add new todo here">
      <input class="btn-primary" type="submit" value="add">
    </form>
  </div>
</div>

  </body>

</html>

/* Put your css in here */

.done-true {
  text-decoration: line-through;
  color: grey;
}