nanoption

Tiny (220 bytes), zero dependency wrapper for nullable values.

TL;DR

// With nanoption
import { Option } from 'nanoption'

function getJwtToken(executionContext) {
  const jwtToken = Option.of(executionContext)
    .map(context => context.switchToHttp()) // context can have no http mod (e.g. WebSocket)
    .map(httpMod => httpMod.getRequest())   // context can have no http request
    .map(request => request.headers)        // request can have no headers
    .map(headers => parseHeaders(headers))  // parseHeaders can return null
    .map(jwtAuth => jwtAuth.split(' ')[1])  // auth header can contain only one part
    .getOrElse('')

  return jwtToken
}

// Without nanoption
function getJwtToken(executionContext) {
  const httpMod = executionContext.switchToHttp()
  if (!httpMod) return ''  // context can have no http mod (e.g. WebSocket)

  const request = httpMod.getRequest()
  if (!request) return ''  // context can have no http request

  const headers = request.headers
  if (!headers) return ''  // request can have no headers

  const jwtAuth = parseHeaders(headers)
  if (!jwtAuth) return ''  // headers can have no auth header

  const jwtToken = wtAuth.split(' ')[1]
  if (!jwtToken) return '' // auth header can contain only one part
  
  return jwtAuth
}

Installation

yarn add nanoption

Or if you prefer npm:

npm i nanoption

Motivation

It JS in some cases we can get an error Cannot do something of undefined/null. This library explicitly works with nullable values and provide clear interface for it.

Also, library support TypeSciript as first-class citizen and do some checks in complie time. For example:

import { Option } from 'nanoption'

// #map
Option.of(2).map(_ => _ * 2) // Some(4)
Option.of().map(() => 2)     // None (known at compile time)

// #get
Option.of(3).get()           // 3
Option.of().get()            // COMPILE ERROR! Can't call get() on None

Of course, you can use JavaScript without TypeScript, but it's not as fun.

Now Optional Chaining Proposal only on stage 1, but very useful. This library give ECMAScript-version independent alternative for it.

API

import { Option } from 'nanoption'

// Create an option
Option.of(3)                                // Some(3)
Option.of('abc')                            // Some('abc')
Option.of(null)                             // None
Option.of(undefined)                        // None

// #map
Option.of(2).map(_ => _ * 2)                // Some(4)
Option.of().map(() => 2)                    // None

// #flatMap
Option.of(3).flatMap(_ => Option.of(_ * 2)) // Some(6)
Option.of().flatMap(() => Option.of(2))     // None

// #get
Option.of(3).get()                          // 3
Option.of().get()                           // throw Exception

// #getOrElse
Option.of(1).getOrElse(2)                   // 1
Option.of(null).getOrElse(2)                // 2

// #isEmpty
Option.of(2).isEmpty()                      // false
Option.of().isEmpty()                       // true

// #nonEmpty
Option.of(2).nonEmpty()                     // true
Option.of().nonEmpty()                      // false

// #toString
Option.of(2).toString()                     // "Some(2)"
Option.of().toString()                      // "None"

Alternatives

• tsoption is Fantasyland-compliant, but it requires 2-3 times more space.