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Defining Profiles

Each profile defines a value for sourceKey and destinationKey. These keys must extend string and should be unique combinations, beyond that the choice is irrelevant to the function of Kitbag Mapper.

Profiles can be defined with createProfile utility

import { createProfile } from '@kitbag/mapper'

const profiles = [
  createProfile('number', 'string', (source: number): string => source.toString()),
  createProfile('number', 'Date', (source: number): Date => new Date(source)),

or using the Profile type

import { Profiles } from '@kitbag/mapper'

export const profiles = [
    sourceKey: 'number',
    destinationKey: 'string',
    map: (source: number): string => {
      return source.toString()
    sourceKey: 'number',
    destinationKey: 'Date',
    map: (source: number): Date => {
      return new Date(source)
] as const satisfies Profiles

Here is a simple example of a profile that converts a server model you might see in an API service to the frontend model.

import { Profile } from '@kitbag/mapper'
import { UserApiResponse, User } from '@/types'

export const userApiResponseToUser = {
  sourceKey: 'UserApiResponse',
  destinationKey: 'User',
  map: (source: UserApiResponse): User => {
    return {
      email: source.email_address,
      isActive: source.is_active,
      createdDate: new Date(source.created_date),
} as const satisfies Profile
import { ObjectId } from 'mongodb'

export type UserApiResponse = {
  id: ObjectId,
  email_address: string,
  is_active: boolean,
  created_date: string,
export type User = {
  id: string,
  email: string,
  isActive: boolean,
  createdDate: Date,

The real magic happens inside of the map function of your profile. The types you define for the source argument and the the return type are what will ultimately provide the type safety when is called.

Satisfies Operator

Note the satisfies operator requires Typescript v4.9+.