What is Option in fp-ts and what does it represent?

Option is a type representing a value that might not exist, expressed as either `Some(value)` for a present value or `None` for an absent one. It helps eliminate null checks and enable safe property access.

How do I create an Option from a nullable value?

Use `O.fromNullable(x)` to convert `null` or `undefined` into `None`, and anything else into `Some(x)`. Alternatively, use `O.some(5)` for a known present value or `O.none` for an absent one.

How do I extract a value from an Option with a fallback?

Use `O.getOrElse(() => default)` to get the inner value or return a default if the Option is `None`. You can also use `O.toNullable` or `O.toUndefined` to convert back to `T | null` or `T | undefined`, or `O.match(onNone, onSome)` to pattern-match both branches.

When should I use Option instead of optional chaining?

Use Option specifically when operations on the optional value need to be chained together (like mapping and flatMapping through multiple steps), rather than for every single nullable access. Optional chaining like `user?.profile?.name ?? 'Guest'` is simpler for straightforward cases but can silently miss checks.

What transformation operations does Option support?

Option supports `O.map(fn)` to transform the inner value, `O.flatMap(fn)` to chain another Option-returning operation, and `O.filter(predicate)` to collapse to `None` when the predicate is false.

Skill

Generate fp-ts Option type code snippets

Name: Option Quick Reference
Availability: OnlineOnly
Author: Antigravity

A compact fp-ts Option cheat sheet for handling nullable and optional values without null checks.

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Why it matters

Leverage the fp-ts Option type for safer, more composable handling of potentially absent values in your TypeScript code. This asset provides quick reference snippets to eliminate null checks and implement safe property access.

Outcomes

What it gets done

Generate fp-ts Option creation code (Some, None, fromNullable, fromPredicate).

Generate fp-ts Option transformation code (map, flatMap, filter).

Generate fp-ts Option extraction code (getOrElse, toNullable, toUndefined, match).

Illustrate common patterns for safe property access and array element retrieval using Option.

Install

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Run in your project directory:

curl -fsSL https://spark.entire.vc/get/ag-fp-option-ref | bash

Overview

Option Quick Reference

A compact fp-ts Option cheat sheet covering creation, transformation, and extraction of nullable values, with patterns for safe property access and array head extraction. Use it as a quick reference for nullable or optional values in fp-ts, when a short reference card is wanted rather than a full migration guide.

What it does

A compact cheat sheet for fp-ts's Option type - a value that might not exist, as Some(value) or None - covering creation (O.some, O.none, O.fromNullable, O.fromPredicate), transformation (O.map, O.flatMap, O.filter), and extraction (O.getOrElse, O.toNullable, O.toUndefined, O.match). It shows common patterns - safe nested property access without optional chaining, and getting an array's first element via A.head as an Option - and contrasts nullable-chaining (user?.profile?.name ?? 'Guest', easy to forget a check) against the same logic as an explicit, composable Option pipe.

import * as O from 'fp-ts/Option'

O.some(5)              // Some(5)
O.none                 // None

When to use - and when NOT to

Use it as a quick reference for nullable or optional values in fp-ts - eliminating null checks, safe property access, or optional chaining - when a short reference card is wanted rather than a full migration guide.

Inputs and outputs

Input: a TypeScript value that may be null, undefined, or missing. Output: an Option<Value> expression using the referenced creation, transform, or extraction functions.

Who it's for

TypeScript developers using fp-ts who want to chain operations on optional values safely and need a fast lookup rather than documentation.

FAQ

Common questions

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