TaskEither

Async operations with error handling for real-world apps

What is TaskEither?

TaskEither combines asynchronous operations (like Promise) with explicit error handling (like Either). It's the go-to type for real-world applications that make API calls, read files, or perform any async operation that might fail.

// Instead of try-catch:
try { const data = await fetch(...) } catch (e) { }

// Use TaskEither:
const data: TaskEither<Error, Data> = fetchData()
Promises
Chaining
Parallel
Error recovery
API calls
⚡

Async + Errors

Handle promises with explicit error types

✅

Type-Safe

Both success and error types are known

🛤️

Railway Pattern

Chain async operations that short-circuit

🚀

Production Ready

Perfect for real-world API calls

TaskEither in Action

❌ Try-Catch Hell

async function getUser(id: number) {
  try {
    const response = await fetch(`/api/users/${id}`)
    const user = await response.json()
    return user
  } catch (error) {
    console.error(error)
    return null
  }
}

✅ TaskEither Approach

const getUser = (id: number): TaskEither<Error, User> =>
  pipe(
    TE.tryCatch(
      () => fetch(`/api/users/${id}`),
      E.toError
    ),
    TE.chain(res => TE.tryCatch(() => res.json(), E.toError))
  )

// Errors in types, composable

Practice Exercises

1

Basic

Learn about basic in fp-ts taskeither

beginnerStart
2

From Promise

Learn about from promise in fp-ts taskeither

beginnerStart
3

Chaining

Learn about chaining in fp-ts taskeither

beginnerStart
4

Map

Learn about map in fp-ts taskeither

intermediateStart
5

Fold

Learn about fold in fp-ts taskeither

intermediateStart
6

Recovery

Learn about recovery in fp-ts taskeither

intermediateStart
7

Sequencing

Learn about sequencing in fp-ts taskeither

advancedStart
8

Parallel

Learn about parallel in fp-ts taskeither

advancedStart
9

Api

Learn about api in fp-ts taskeither

advancedStart
10

Pipeline

Learn about pipeline in fp-ts taskeither

advancedStart

Why Learn TaskEither?

⚙️

Master TaskEither

Learn the fundamental concepts and patterns that make TaskEither powerful

💪

10 Exercises

Practice with hands-on exercises from intermediate level

🚀

Production Ready

Apply TaskEither patterns to build robust, type-safe applications