Either Quick Reference

Either = success or failure. Right(value) or Left(error).

When to Use

• You need a quick fp-ts reference for typed synchronous error handling.
• The task involves validation, fallible operations, or converting throwing code to Either.
• You want a compact cheat sheet rather than a long tutorial.

Create

import * as E from 'fp-ts/Either'

E.right(value)           // Success
E.left(error)            // Failure
E.fromNullable(err)(x)   // null → Left(err), else Right(x)
E.tryCatch(fn, toError)  // try/catch → Either