fp-ts-errors

name	fp-ts-errors
description	Handle errors as values using fp-ts Either and TaskEither for cleaner, more predictable TypeScript code. Use when implementing error handling patterns with fp-ts.
type	skill
created	2026-02-27T00:00:00.000Z
domain	software-development
category	languages
risk	safe
source	https://github.com/whatiskadudoing/fp-ts-skills
tags	["skill","software-development","languages","errors"]

Practical Error Handling with fp-ts

This skill teaches you how to handle errors without try/catch spaghetti. No academic jargon - just practical patterns for real problems.

When to Use This Skill

• When you want type-safe error handling in TypeScript
• When replacing try/catch with Either and TaskEither patterns
• When building APIs or services that need explicit error types
• When accumulating multiple validation errors

The core idea: Errors are just data. Instead of throwing them into the void and hoping someone catches them, return them as values that TypeScript can track.

---

1. Stop Throwing Everywhere

The Problem with Exceptions

Exceptions are invisible in your types. They break the contract between functions.

// What this function signature promises:
function getUser(id: string): User

// What it actually does:
function getUser(id: string): User {
  if (!id) throw new Error('ID required')
  const user = db.find(id)
  if (!user) throw new Error('User not found')
  return user
}

// The caller has no idea this can fail
const user = getUser(id) // Might explode!

You end up with code like this:

// MESSY: try/catch everywhere
function processOrder() {
   order
   {
    order = (orderId)
  }  (e) {
    .()
     
  }

   user
   {
    user = (order.)
  }  (e) {
    .()
     
  }

   payment
   {
    payment = (user., order.)
  }  (e) {
    .()
     
  }

   { order, user, payment }
}