fp-types-ref

name	fp-types-ref
description	Quick reference for fp-ts types. Use when user asks which type to use, needs Option/Either/Task decision help, or wants fp-ts imports.
type	skill
created	2026-02-27T00:00:00.000Z
domain	communication-content
category	documentation
risk	safe
source	community
tags	["skill","communication-content","documentation","types","ref"]

fp-ts Quick Reference

When to Use

• You need help choosing between Option, Either, Task, TaskEither, or related fp-ts types.
• The task is about imports, decision guidance, or selecting the right abstraction for a TypeScript flow.
• You want a compact reference for common fp-ts type choices and patterns.

Which Type Should I Use?

Is the operation async?
├─ NO: Does it involve errors?
│   ├─ YES → Either<Error, Value>
│   └─ NO: Might value be missing?
│       ├─ YES → Option<Value>
│       └─ NO → Just use the value
└─ YES: Does it involve errors?
    ├─ YES → TaskEither<Error, Value>
    └─ NO: Might value be missing?
        ├─ YES → TaskOption<Value>
        └─ NO → Task<Value>

Common Imports

// Core
import { pipe, flow } from 'fp-ts/function'

// Types
import * as O from 'fp-ts/Option'      // Maybe exists
import * as E from 'fp-ts/Either'      // Success or failure
import * as TE from 'fp-ts/TaskEither' // Async + failure
import * as T from 'fp-ts/Task'        // Async (no failure)
import * as A from 'fp-ts/Array'       // Array utilities

One-Line Patterns

Need	Code
Wrap nullable