Do Something And Continue Class Execution

I want to add some headers before calling $http's get method. I tried this:

$http = $originalHttpMethod;
this.$http = function() {
   //add headers
   return $http
};
$http.get({url:'http://...'});

but i get this error:

TypeError: Object function () {return $http} has no method 'get'.

I want to do this without crash original class.
How can i done this ?

Make a service instead of doing anything local. This way you can reuse it much easier across your application.

module.factory('$myHttp', ['$http', function($http) {
  //do your stuff
  return $http;
}]);

And then inside your controllers, directives or any other services, just include it as a dependency and use it like so:

$myHttp.get()

Here's some more info about that:

http://www.yearofmoo.com/2012/10/more-angularjs-magic-to-supercharge-your-webapp.html#you-should-be-using-custom-services

You can define your headers in the config parameter object when you call the $http service:

configObj = {url:'http://...', headers: { add your headers here}, ... };
$http.get(configObj);