Data Migration Technique

migrate.js

// prop - destination key
// value - source key
const entityProps = {
  name: 'title',
  body: 'description',
  day: 'date',
  room: 'location',
};

// transform a destination value
// use entire entity to return a transformed value
const entityTransforms = {
  title: entity => entity.title.toLowerCase(),
  room: entity => ({ name: entity.location.name }),
};

// gets a converted entity based on an entityProps object
const getConvertedEntity = (sourceEntity, props, ignore = []) => {
  Object.keys(sourceEntity).reduce((result, key) => {
    if (sourceEntity[key] && !ignore.includes(key)) {
      Object.assign(result, {
        [props[key]] : entityTransforms[key] ? entityTransforms[key](sourceEntity) : sourceEntity[key]
      });
    }
    return result;
  }, {});
};


// example usage
// pretend sourceClient & destClient are 2 different api clients
(async () => {
  
  //list of things from an api
  const apiResponse = await sourceClient.getThings();
  
  //convert each entity in the list
  const convertedEntities = apiResponse.map(entity => {
    const newEntity = getConvertedEntity(entity, entityProps);
    return destClient.createNewThing(newEntity);
  });
  
  //create via api
  await Promise.all(
    apiResponse.map(entity => {
      const newEntity = getConvertedEntity(entity, entityProps);
      return destClient.createNewThing(newEntity);
    })
  );

})();