optics-ts

optics-ts provides type-safe, ergonomic, polymorphic optics for TypeScript

• Many optic types: lens, prism, traversal, getter, affine fold, fold, setter
• Optics for operating on multiple data types: objects, arrays, discriminated unions, strings.
• Removable optics: Allow removing items from containers.
• Ergonomic API: No boilerplate, concise naming.
• Type-safe: The compiler will type check all operations you do. No any, ever.
• Most optics are fully polymorphic: You can write a different data type and still get full type safety.
• Supports both ES6 and CommonJS modules in a single code base.
• Tree shaking support with standalone optics (see The Two Syntaxes).

Example

Method chaining

import * as O from 'optics-ts'

type Book = {
  title: string
  isbn: string
  author: {
    name: string
  }
}

// Create a lens that focuses on author.name
const optic = O.optic_<Book>()
  .prop('author')
  .prop('name')

// This is the input data
const input: Book = {
  title: "The Hitchhiker's Guide to the Galaxy"
  isbn: "978-0345391803",
  author: {
    name: "Douglas Adams"
  }
}

// Read through the optic
O.get(optic)(input)
// "Douglas Adams"

// Write through the optic
O.set(optic)("Arthur Dent")(input)
// {
//   title: "The Hitchhiker’s Guide to the Galaxy"
//   isbn: "978-0345391803",
//   author: {
//     name: "Arthur Dent"
//   }
// }

// Update the existing value through the optic, while also changing the data type
O.modify(optic)(str => str.length + 29)(input)
// {
//   title: "The Hitchhiker’s Guide to the Galaxy"
//   isbn: "978-0345391803",
//   author: {
//     name: 42
//   }
// }

Standalone

import * as O from 'optics-ts/standalone'

// Create a lens that focuses on author.name
const optic = O.compose('author', 'name')

// This is the input data
const input = {
  title: "The Hitchhiker's Guide to the Galaxy"
  isbn: "978-0345391803",
  author: {
    name: "Douglas Adams"
  }
}

// Read through the optic
O.get(optic, input)
// "Douglas Adams"

// Write through the optic
O.set(optic, "Arthur Dent", input)
// {
//   title: "The Hitchhiker’s Guide to the Galaxy"
//   isbn: "978-0345391803",
//   author: {
//     name: "Arthur Dent"
//   }
// }

// Update the existing value through the optic, while also changing the data type
O.modify(optic, (str) => str.length + 29, input)
// {
//   title: "The Hitchhiker’s Guide to the Galaxy"
//   isbn: "978-0345391803",
//   author: {
//     name: 42
//   }
// }

For more information about the differences between the method chaining and standalone syntaxes, see The Two Syntaxes.