function mapObject(object, callback, context) {
  if (!object) {
    return null;
  }
  var result = {};
  for (var name in object) {
    if (hasOwnProperty.call(object, name)) {
      result[name] = callback.call(context, object[name], name, object);
    }
  }
  return result;
}
Executes the provided `callback` once for each enumerable own property in the
object and constructs a new object from the results. 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 `mapObject` 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 `mapObject` visits them.
Properties that are deleted before being visited are not visited.

@grep function objectMap()
@grep function objMap()

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