BeforeMap

As the name suggests, beforeMap() sets up a MapCallback to be called before the map operation.

Configure on Mapping

Pass beforeMap() in createMap() to sets up the MapCallback

createMap(
    mapper,
    User,
    UserDto,
    beforeMap((source, destination) => {})
);

Configure on map()

Pass beforeMap in MapOptions when calling map() to sets up the MapCallback

mapper.map(user, User, UserDto, {
    beforeMap: (source, destination) => {},
});

info

• beforeMap() on map() has precedence over Mapping
• For mapArray (and its variants), beforeMap() on Mapping is ignored because it would be bad for performance if we run beforeMap for each and every item of the array. beforeMap() on mapArray() will be invoked with (sourceArray, []) instead

What about preMap?

When create the Mapper, we can customize the preMap function on the MappingStrategy. The differences between preMap and beforeMap are:

• preMap runs before every map operation
• There is only one preMap per Mapper
• preMap runs BEFORE beforeMap