ts-known

If you're looking for a ultra-light and non-intrusive utility library to conveniently and safely handle unknown variables in your TypeScript projects, ts-known can help. With a collection of guards for common types and functions to generate type-specific guards, ts-known allows for easy handling of unknown variables caught by try-catch, network-transmitted data, and parsed JSON objects.

Installation

To install ts-known, simply use your favorite package manager:

npm install ts-known
# or
yarn add ts-known

Features

Provides a collection of guards for common types
Allows you to generate type-specific guards with ease
Ensures your code is safe when handling unknown type variables
Supports handling of circular references
Easy to use and integrate into your TypeScript project

Usage

Using ts-known is easy. Simply import the library and start using its guards:

import { isIterator } from 'ts-known'

const x: unknown

if (isIterator(x)) {
  // x is now guaranteed to be a iterator
}

ts-known provides operators and guards that can be easily used together with your own type guards. For example, consider the following types and type guard.

type Person = {
  name: string;
  friend: Dog;
};

class Dog {}

function isDog(x: unknown): x is Dog {
  return x instanceof Dog;
}

const guard = objectOf({
  name: isString,
  friend: isDog,
})

const x: unknown = {}

if (guard(x)) {
  type Name = typeof x.name // string
  type Friend = typeof x.friend // Dog
}

In addition to the provided guards, you can also generate your own type-specific guards.

objectOf

objectOf is a function that takes an object with property names and associated guards as arguments and returns a function that checks if an object has properties guarded by given guards. If the object has a circular reference, SELF should be used as the guard.

import { objectOf, isString, isNumber, SELF } from 'ts-known'

type Elem = {
  name: string
  ref: Elem
}

function handleElem(x: Elem) {}

const guard = objectOf({
  name: isString,
  ref: optional(SELF),
})

const elem: unknown = { name: 'element' }
console.log(guard(elem)) // true

elem.ref = 1
console.log(guard(elem)) // false

elem.ref = elem
console.log(guard(elem)) // true

handleElem(elem) // TS: Argument of type 'unknown' is not assignable to parameter of type 'Elem'.

if (guard(elem)) {
  handleElem(elem) // 🎉
}

arrayOf

arrayOf is a function that takes a spread of guards as arguments and returns a function that checks if an array contains only elements that match one of the given guards.

import { arrayOf, isString, isNumber } from 'ts-known'

const guard = arrayOf(isNumber, isString)

console.log(guard([1])) // true
console.log(guard([1, 'hello'])) // true
console.log(guard(['1', 'hello', '1', 'hello'])) // true
console.log(guard([true])) // false
console.log(guard([1, 'hello', true])) // false

or

or is a function that takes a spread of guards as arguments and returns a function that checks if a value matches any of the given guards.

import { or, isString, isNumber, isBoolean } from 'ts-known'

const guard = or(isString, isNumber, isBoolean)

console.log(guard('foo')) // true
console.log(guard(123)) // true
console.log(guard(true)) // true
console.log(guard(undefined)) // false
console.log(guard(null)) // false
console.log(guard({})) // false
console.log(guard([])) // false

and

and is a function that takes a spread of guards as arguments and returns a function that checks if a value matches all of the given guards.

import { and, objectOf, isObject, isString, isNumber } from 'ts-known'

const guard = and(
  isObject,
  objectOf({ name: isString }),
  objectOf({ age: isNumber })
)

console.log(guard({ name: 'Luci', age: 17 })) // true
console.log(guard(undefined)) // false
console.log(guard(null)) // false
console.log(guard({ name: 'Luci' })) // false
console.log(guard({ age: 30 })) // false
console.log(guard({ name: 123 })) // false
console.log(guard({ name: 'Luci', age: '17' })) // false

optional

optional is a function that takes a guard as an argument and returns a function that checks if a value is either undefined or matches the given guard.

const guard = and(
  isObject,
  objectOf({
    name: optional(isString),
  }),
  objectOf({
    age: optional(isNumber),
  })
)

console.log(guard({ name: 'Luci', age: 17 })) // true
console.log(guard({ name: 'Luci' })) // true
console.log(guard({ age: 17 })) // true
console.log(guard({})) // true
console.log(guard(undefined)) // false
console.log(guard(null)) // false
console.log(guard({ name: 'Luci', age: '17' })) // false
console.log(guard({ name: 17 })) // false

Contribution

We welcome any contributions to ts-known! Feel free to create a pull request, report a bug, or suggest new features. We appreciate your support!

License

ts-known is licensed under the MIT license.

LuciNyan/ts-known