simplytyped

SimplyTyped

Yet another typing library. This differs by aiming to be less experimental than others, driven by industry use cases.

Many of the exposed types are a very thin layer above built in functionality. The goal is to provide all of the building blocks necessary to make concise, yet complex types.

Conditionals

Some (somewhat common) implementations of conditional type logic

If

type x = If<True, string, number> // => string
type y = If<False, string, number> // => number

And

type x = If<And<True, True>, string, number> // => string
type y = If<And<True, False>, string, number> // => number
...

Or

type x = If<Or<True, False>, string, number> // => string
type y = If<Or<False, False>, string, number> // => number
...

Not

type x = Not<True> // => False
type y = Not<False> // => True

Objects

type obj1 = { w: string, x: string, y: number }
type obj2 = { y: string, z: number }

Keys

No different than keyof, but can look a bit nicer when nesting many types deep

type x = keyof obj1 // => 'w' | 'x' | 'y'
type y = Keys<obj1> // => 'w' | 'x' | 'y'

ObjectType

On its own, not that interesting. Takes an object and makes it an object type. Is useful when combined with & intersection types (as seen next).

type x = ObjectType<obj1> // => { w: string, x: string, y: number }

CombineObjects

Takes the intersection between two objects, and flattens them. This can make extremely complex types look much nicer.

type x = obj1 & obj2 // => { w: string, x: string, y: number } & { y: string, z: number }
type y = CombineObjects<obj1, obj2> // => { w: string, x: string, y: string & number, z: number }

SharedKeys

Gets all of the keys that are shared between two objects (as in keys in common).

type x = SharedKeys<obj1, obj2> // => 'y'

DiffKeys

Gets all of the keys that are different from obj1 to obj2.

type x = DiffKeys<obj1, obj2> // => 'w' | 'x'
type y = DiffKeys<obj2, obj1> // => 'z'

AllKeys

Gets all keys between two objects.

type x = AllKeys<obj1, obj2> // => 'w' | 'x' | 'y' | 'z'

Omit

Gives back an object with listed keys removed.

type x = Omit<obj1, 'w' | 'x'> // => { y: number }

Merge

Much like _.merge in javascript, this returns an object with all keys present between both objects, but conflicts resolved by rightmost object.

type x = Merge<obj1, obj2> // => { w: string, x: string, y: string, z: number }

DeepPartial

Uses Partial to make every parameter of an object optional (| undefined).

type x = DeepPartial<obj1> // => { w?: string, x?: string, y?: number }

Tuples

A tuple can be defined in two ways: [number, string] which as of Typescript 2.7 has an enforced length type parameter: [number, string]['length'] === 2 or using this libraries Tuple<any> which can be extended with any length of tuple: function doStuff<T extends Tuple<any>>(x: T) {}.

Tuple

function doStuff<T extends Tuple<any>>(x: T) {}

doStuff(['hi', 'there']); // => doStuff(x: ['hi', 'there']): void

UnionizeTuple

type x = UnionizeTuple<[number, string]> // => number | string

Strings

Diff

Get the differences between two unions of strings.

type x = Diff<'hi' | 'there', 'hi' | 'friend'> // => 'there'