Update TypeORM entity fields from a NestJS DTO object

repository.util.ts

/**
 * Set defined/scalar entity fields from a DTO (only using fields existing on entity)
 *
 * NOTE: Mutates original value!
 *
 * NOTE: Skips all non-scalar fields and `undefined` DTO values, which would other wise cause unexpected
 *         data loss for non-specified or partially provided relation values. However, non-scalar fields
 *         can be permitted with `allowNonScalarKeys` if specifically handled/provided.
 *
 * @param options.allowNonScalarKeys - Allows non-scalar keys to be assigned (ie. arrays, objects, etc)
 * @param options.omitKeys - Keys to omit from assigning to entity (ie. ids, etc)
 * @param options.onlyKeys - Keys to allow assigning to entity (skips others if specified!)
 *
 * @returns Entity with updated scalar fields
 *
 * @example
 * const supplier = await this.supplierRepo.findOne({where: {id}});
 * setEntityFieldsFromDto(supplier, payload, {omitKeys: ["id"]});
 * supplier = await this.supplierRepo.save(supplier);
 */
export const setEntityFieldsFromDto = <T extends BaseEntity>(
  entity: T,
  dto: ClassInstance,
  options: {
    allowNonScalarKeys?: (keyof T)[];
    omitKeys?: (keyof T)[];
    onlyKeys?: (keyof T)[];
  } = {},
): T => {
  const {omitKeys, onlyKeys} = options;

  Object.keys(entity).forEach((key) => {
    const entityKey = key as keyof typeof entity;
    const entityValue = entity[entityKey];
    const dtoValue = dto[entityKey as string];

    // Skip entity properties missing from DTO object, specifically omitted keys, or non-whitelisted keys (if whitelisting)
    if (
      dtoValue === undefined ||
      omitKeys?.includes(entityKey) ||
      (onlyKeys && !onlyKeys.includes(entityKey))
    ) {
      return;
    }

    // Skip non-scalar values (to avoid incorrect replacements/merges), unless specified with 'allowNonScalarKeys'
    if (
      isArray(entityValue) ||
      isArray(dtoValue) ||
      (isObject(entityValue) && !(entityValue instanceof Date)) ||
      (isObject(dtoValue) && !(dtoValue instanceof Date))
    ) {
      // Ensure that only allowed non-scalar keys that are actually set on DTO will update the entity!
      if (!options.allowNonScalarKeys?.includes(entityKey) || dtoValue === undefined) {
        return;
      }
    }

    entity[entityKey] = dtoValue as typeof entityValue;
  });

  return entity;
};