Security News
The Dark Side of Open Source
At Node Congress, Socket CEO Feross Aboukhadijeh uncovers the darker aspects of open source, where applications that rely heavily on third-party dependencies can be exploited in supply chain attacks.
newtype-ts
Advanced tools
Changelog
0.3.5
Readme
To install the stable version:
npm i newtype-ts
Note. newtype-ts
depends on fp-ts
and monocle-ts
, starting from 0.3.0
you must install both fp-ts
and monocle-ts
manually (fp-ts
and monocle-ts
are listed in peerDependency
)
A common programming practice is to define a type whose representation is identical to an existing one but which has a separate identity in the type system.
type USD = number
type EUR = number
const myamount: USD = 1
declare function change(usd: USD): EUR
declare function saveAmount(eur: EUR): void
saveAmount(change(myamount)) // ok
saveAmount(myamount) // opss... this is also ok because both EUR and USD are type alias of number!
Let's define a newtype for the EUR currency
import { Newtype, iso } from 'newtype-ts'
interface EUR extends Newtype<{ readonly EUR: unique symbol }, number> {}
// isoEUR: Iso<EUR, number>
const isoEUR = iso<EUR>()
// myamount: EUR
const myamount = isoEUR.wrap(0.85)
// n: number = 0.85
const n = isoEUR.unwrap(myamount)
declare function saveAmount(eur: EUR): void
saveAmount(0.85) // static error: Argument of type '0.85' is not assignable to parameter of type 'EUR'
saveAmount(myamount) // ok
By definition a "newtype" must have the exact same runtime representation as the value that it stores, e.g. a value of type EUR
is just a number
at runtime.
For the Iso
type, see the monocle-ts documentation.
An Integer
is a refinement of number
import { Newtype, prism } from 'newtype-ts'
interface Integer extends Newtype<{ readonly Integer: unique symbol }, number> {}
const isInteger = (n: number) => Number.isInteger(n)
// prismInteger: Prism<number, Integer>
const prismInteger = prism<Integer>(isInteger)
// oi: Option<Integer>
const oi = prismInteger.getOption(2)
declare function f(i: Integer): void
f(2) // static error: Argument of type '2' is not assignable to parameter of type 'Integer'
oi.map(f) // ok
For the Prism
type, see the monocle-ts documentation.
Char
Integer
Negative
NegativeInteger
NonNegative
NonNegativeInteger
NonPositive
NonPositiveInteger
NonEmptyString
NonZero
NonZeroInteger
Positive
PositiveInteger
import { NonZero, prismNonZero } from 'newtype-ts/lib/NonZero'
// a total function
const safeDivide = (numerator: number, denominator: NonZero): number => {
return numerator / prismNonZero.reverseGet(denominator)
}
// result: Option<number>
const result = prismNonZero.getOption(2).map(denominator => safeDivide(2, denominator))
The stable version is tested against TypeScript 3.5.1
newtype-ts version | required typescript version | required fp-ts version | required monocle-ts version |
---|---|---|---|
0.3 | 3.5.1+ | 2.0.0-rc.6+ | 2.0.0-rc.1+ |
<= 0.2.4 | 2.8+ | 1.0.0+ | 1.0.0+ |
const double = n => n * 2
const doubleEUR = eurIso.modify(double)
Test double(2)
vs doubleEUR(eurIso.wrap(2))
Results (node v8.9.3
)
double x 538,301,203 ops/sec ±0.45% (87 runs sampled)
doubleEUR x 536,575,600 ops/sec ±0.27% (87 runs sampled)
const double = (n: number): number => n * 2
// doubleEUR: (s: EUR) => EUR
const doubleEUR = eurIso.modify(double)
FAQs
Implementation of newtypes in TypeScript
The npm package newtype-ts receives a total of 226,175 weekly downloads. As such, newtype-ts popularity was classified as popular.
We found that newtype-ts demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
Did you know?
Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
Security News
At Node Congress, Socket CEO Feross Aboukhadijeh uncovers the darker aspects of open source, where applications that rely heavily on third-party dependencies can be exploited in supply chain attacks.
Research
Security News
The Socket Research team found this npm package includes code for collecting sensitive developer information, including your operating system username, Git username, and Git email.
Security News
OpenJS is warning of social engineering takeovers targeting open source projects after receiving a credible attempt on the foundation.