whole_func_string: function (key, value, keep) {
  
              // Get storage type
              keep = (typeof keep === 'undefined' || typeof keep !== 'boolean') ? false : keep;
              var storageType = keep ? 'localStorage' : 'sessionStorage';
  
              // Convert undefined values to null
              if (angular.isUndefined(value)) {
                  value = null;
              } else if (angular.isObject(value) || angular.isArray(value)) {
                  value = angular.toJson(value);
              }
  
              // Set web storage
              webStorage = $window[storageType];
  
              // Add data to storage
              webStorage.setItem(key, value);
  
              return true;
          }
func_code_string: function (key, value, keep) {
  
              // Get storage type
              keep = (typeof keep === 'undefined' || typeof keep !== 'boolean') ? false : keep;
              var storageType = keep ? 'localStorage' : 'sessionStorage';
  
              // Convert undefined values to null
              if (angular.isUndefined(value)) {
                  value = null;
              } else if (angular.isObject(value) || angular.isArray(value)) {
                  value = angular.toJson(value);
              }
  
              // Set web storage
              webStorage = $window[storageType];
  
              // Add data to storage
              webStorage.setItem(key, value);
  
              return true;
          }
func_documentation_string: /*
  Add value to storage
  - key: key to retrieve data
  - value: value of data
  - keep: *optional* boolean to keep value indefinitly (localStorage) or temporarily (sessionStorage)