AngularJS 1.4.x + RxJS

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

app.controller('MainCtrl', function($scope, rx) {
  $scope.counter;
  $scope.buttonEnabled = true;

  var observable = rx.Observable
    .interval(1000)
    .take(3)
    .safeApply($scope, function(x) { 
      $scope.counter = x; 
    });
  
  $scope.click = function(){
    // angular.noop is just a shorthand for an empty function function(){}
    
    observable.subscribe(
      function onNext(value){
        console.log(value);
      }, // onNext
      angular.noop, // onError
      function onCompleted(){
        console.log('Completed');
        $scope.$apply(function(){
          $scope.buttonEnabled = false;
        })
    });
    //forEach is an alias for subscribe 
    // o.forEach(function(){});
  }
   
});

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

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link rel="stylesheet" href="style.css" />
    <script data-require="angular.js@1.4.x" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.5/angular.min.js" data-semver="1.4.5"></script>
    <script data-require="rxjs@*" data-semver="2.5.3" src="//cdnjs.cloudflare.com/ajax/libs/rxjs/2.5.3/rx.all.js"></script>
    <script data-require="rx.angular.js@*" data-semver="0.0.14" src="https://cdn.rawgit.com/Reactive-Extensions/rx.angular.js/v0.0.14/dist/rx.angular.js"></script>
    <script src="app.js"></script>
  </head>

<body ng-controller="MainCtrl">
  <button ng-click="click()" ng-disabled="!buttonEnabled">Start</button>
  <span>{{counter}}</span>
</body>

</html>

body {
  font-size: 10em;
}