function filterObject(object, callback, context) {
  if (!object) {
    return null;
  }
  var result = {};
  for (var name in object) {
    if (hasOwnProperty.call(object, name) &&
        callback.call(context, object[name], name, object)) {
      result[name] = object[name];
    }
  }
  return result;
}
Executes the provided `callback` once for each enumerable own property in the
object and constructs a new object of all the values for which `callback`
returns a true value. The `callback` is invoked with three arguments:

 - the property value
 - the property name
 - the object being traversed

Properties that are added after the call to `filterObject` will not be
visited by `callback`. If the values of existing properties are changed, the
value passed to `callback` will be the value at the time `filterObject`
visits them. Properties that are deleted before being visited are not
visited.

@grep function objectFilter()
@grep function objFilter()

@param {?object} object
@param {function} callback
@param {*} context
@return {?object}