Decorators in AngularJS, $provide.decorator

$provide.decorator if defined in config section of the application code and modifies original object which is passed as $delegate argument into decorator.

Here is set of examples giving better view on a powerful feature of decorators, available in AngularJS:

• adding a custom method to 3rd party service,  by tamakisquare - http://plnkr.co/edit/lj9srM2KXZmwmTxLb1p7?p=preview
• logging time while the async call is performed, using Promise.always - by K. Scott Allen http://odetocode.com/blogs/scott/archive/2013/06/06/decorating-angularjs-services.aspx  
• creating more detailed response description, https://egghead.io/lessons/angularjs-provide-decorator
• adding custom method reload method to $state provider - stackoverflow.com/a/23198743/405623

MY_APP.config(function($provide) {
  $provide.decorator('DECORATOR_NAME', function($delegate) {

//directly add methods
    $delegate.NEW_METHOD = function(...) {
      //do stuff
    };

//or using object prototype 
Object.defineProperty($delegate.prototype, 'NEW_METHOD', 

{ 

 get: function() { 

//do stuff

 } 

 });    return $delegate;
  });

});