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// If you need to create a text dictionary with not all of it keys | |
type TermDictionary<TKey extends string> = Partial<Record<TKey, string>>; | |
type StatusUnion = 'Success' | 'Error' | 'Unknown'; | |
enum StatusEnum { | |
Success, | |
Error, | |
Unknown, |
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type Key<T extends object> = keyof T; | |
type Keys<T extends object> = Array<Key<T>>; | |
function keysOf<T extends object>(value: T): Keys<T> { | |
const keys: string[] = Object.keys(value); | |
return keys as Keys<T>; | |
} |
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type Swap<T, USubject, UTarget> = T extends USubject ? Exclude<T, USubject> | UTarget : T; | |
type Whatever = string | null; | |
// Swap null to undefined | |
type Swapped = Swap<Whatever, null, undefined>; // string | undefined | |
// TODO: Make a nested object implementation |
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// Extendable regular object | |
type Extends<T extends object> = T & Record<string, unknown>; | |
// Extendable object with extendable nested objects | |
type Extendable<T> = Extends<{ [Key in keyof T]: T[Key] extends object ? Extends<T[Key]> : T[Key] }>; | |
type Employee = { | |
name: string, | |
age: number, |
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// Unreliable object 😱 | |
type UnsafePerson = { | |
name?: string | null, | |
age?: number | null, | |
} | |
// Nested unreliable object 😱😱😱 | |
type UnsafeParent = UnsafePerson & { child: UnsafePerson }; | |
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type SizeToken = 'XSmall' | 'Small' | 'Medium' | 'Large' | 'XLarge'; | |
type ElementSizeVariant<T = string> = T extends SizeToken ? T | 'Medium' : { width: number, height: number }; | |
type ButtonSize = ElementSizeVariant<'Small' | 'Large'>; // 'Small' | 'Large' | 'Medium'; | |
type CardSize = ElementSizeVariant; // { width: number, height: number } |
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// with infer keyword | |
type ArrayItemInfer<T> = T extends Array<infer I> ? I : never; | |
// or just with regular index type 🙃 | |
type ArrayItemRegular<T extends Array<any>> = T[number]; | |
type People = { firstName: string; lastName: string; }[]; | |
type PersonInfer = ArrayItemInfer<People>; // { firstName: string; lastName: string; } ✅ |
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type Validator<T> = (value: T) => boolean; | |
class FormInput<T> { | |
constructor(public value: T, public validators: Validator<T>[]){} | |
get isValid(): boolean { | |
return this.validators.every(v => v(this.value)); | |
} | |
} |
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// Example entity | |
export interface IPerson { | |
firstName: string, | |
lastName: string, | |
age: number, | |
} | |
type SortOrder = 'asc' | 'desc'; // ascending or descending | |
type OrderByKeys<T> = `${keyof T & string}:${SortOrder}`[] |