@fp-ts/optic

A porting of zio-optics to TypeScript

Optics

flowchart TD
  Optic --> Iso
  Iso --> Lens
  Iso --> Prism
  Lens --> Optional
  Prism --> Optional
  Optional --> Getter
  Optional --> Setter

Example

interface Street {
  num: number;
  name: string;
}
interface Address {
  city: string;
  street: Street;
}
interface Company {
  name: string;
  address: Address;
}
interface Employee {
  name: string;
  company: Company;
}

Let's say we have an employee and we need to upper case the first character of his company street name. Here is how we could write it in vanilla TypeScript

const employee: Employee = {
  name: "john",
  company: {
    name: "awesome inc",
    address: {
      city: "london",
      street: {
        num: 23,
        name: "high street",
      },
    },
  },
};

const capitalize = (s: string): string =>
  s.substring(0, 1).toUpperCase() + s.substring(1);

const employeeCapitalized = {
  ...employee,
  company: {
    ...employee.company,
    address: {
      ...employee.company.address,
      street: {
        ...employee.company.address.street,
        name: capitalize(employee.company.address.street.name),
      },
    },
  },
};

As we can see copy is not convenient to update nested objects because we need to repeat ourselves. Let's see what could we do with @fp-ts/optic

import * as Optic from "@fp-ts/optic";

const _name = Optic.id<Employee>()
  .compose(Optic.key("company"))
  .compose(Optic.key("address"))
  .compose(Optic.key("street"))
  .compose(Optic.key("name"));

const capitalizeName = Optic.modify(_name)(capitalize);

expect(capitalizeName(employee)).toEqual(employeeCapitalized);

Installation

To install the alpha version:

npm install @fp-ts/optic

Documentation

• API Reference

License

The MIT License (MIT)

Changelog

0.0.1

Patch Changes

• #5 2e29f77 Thanks @gcanti! - Implement compose as fluent to improve overload selection