Caching a promise in a reproduceable way

gistfile1.js

function cachedPromising(){
  var def = $q.defer();
  if(!cachedPromising.cached_value)
    promising().then(function(data){cachedPromising.cached_value = data; def.resolve(cachedPromising.cached_value) });
  else def.resolve(cachedPromising.cached_value);
  return def.promise;
}