Creating an AngularJS Decorator without using the object.defineProperty method.Alternatively

Is there a way to implement decorators without relying on object.defineProperty?

I have explored the shims that are available:

If these options do not work, are there alternative methods for utilizing decorators as intended?

I am specifically using the decorator for $onRootScope.

My framework of choice is angular 1.08 and I require compatibility with IE7.

Update

I have experimented with various techniques that appear to be effective, but I am unsure about their distinctions: plunkr

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

app.config(['$provide', function($provide){
  $provide.decorator('$rootScope', ['$delegate', function($delegate){
    $delegate.a = 1;
    $delegate.constructor.prototype.b = 2;
    Object.defineProperty($delegate.constructor.prototype, 'c', {
      value: 3
    });
    return $delegate;
  }]);
}]);

app.controller('MainCtrl', function($rootScope, $scope) {
  console.log($rootScope);   //reveals `a` property
  console.log($rootScope.constructor.prototype); //=> {b:2, c:3}
  console.log($rootScope.a); //=> 1
  console.log($rootScope.b); //=> 2
  console.log($rootScope.c); //=> 3
  $scope.name = 'World';
});

Thank You.

Answer №1

One way to approach the code snippet you provided is by using the following solution:

var proto = Object.getPrototypeOf(Object.getPrototypeOf($delegate));
proto['$onRootScope'] = function (name, listener) {
   var unsubscribe = $delegate.$on(name, listener);
   this.$on('$destroy', unsubscribe);
};

In the original code snippet, the line $delegate.constructor.prototype grants access to the prototype of $delegate.

Once you have access to it, you can easily define a new function without necessarily resorting to the use of defineProperty. The only downside is that when using defineProperty, you have the option to configure the method as non-enumerable (meaning it won't show up in for-each loops). By opting for this alternative method, the added method will be visible in for-each loops. This might not pose an issue for your specific scenario.

To showcase this concept, I have prepared a demo on JSFiddle.

If the getObjectPrototypeOf function is unavailable in your browser, you can utilize John Resig's polyfill:

if ( typeof Object.getPrototypeOf !== "function" ) {
  if ( typeof "test".__proto__ === "object" ) {
    Object.getPrototypeOf = function(object){
      return object.__proto__;
    };
  } else {
    Object.getPrototypeOf = function(object){
      // This may not work properly if the constructor has been altered
      return object.constructor.prototype;
    };
  }
}

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