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https://github.com/lucinyan/ts-known

This library offers guards for common types, and methods to generate type guards for specific types quickly. Safely handle unpredictable unknown types with ease.
https://github.com/lucinyan/ts-known

guard ts type-guards typescript utils

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This library offers guards for common types, and methods to generate type guards for specific types quickly. Safely handle unpredictable unknown types with ease.

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README 

        
# 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:



```bash

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:

```ts

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.

```ts

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.

```ts

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.

```ts

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.

```ts

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.

```ts

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.

```ts

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.