Introduction

error-as-either provides a clean means of expressing error handling that doesn't cause stack unwinding. There are other uses for an Either type, but this particular function will take any result thrown from f and coerce it into an Error if it isn't one already, and then return the Error instead of throwing it. The benefit is that eithers can be composable, and it removes invisible control flow from your program's execution.

It should be noted the result returned here is A | Error where A is whatever the return type of f is. This is not the same thing as Fantasy Land's (Either)[https://github.com/ramda/ramda-fantasy/blob/master/docs/Either.md], but that might be a better thing to do in the future.

Installation

yarn add -E error-as-either

Usage

import errorAsEither from 'error-as-either'

const result = errorAsEither(() => JSON.parse('{'))

if(result instanceof Error) {
  console.error('Input is not valid JSON!')
} else {
  console.log('I got a ', result)
}

Types

All types are expressed as Flow types.

This is the signature for errorAsEither:

<A>(f: () => A): A | Error