typelab

A lab of reusable utility types for everyday TypeScript code.

📝 Table of Contents

• 🤔 About
• 🔌 Installation
• 📔 Docs
  • Showcases
  • All Available Types
• ⛏️ Built Using
• 📄 License

🤔 About

This package offers a suite of versatile utility types that simplify common tasks, improve type safety, and boost productivity.

• Easy to use
• Zero third party dependencies
• Type level only
• No more copy paste "type definitions" between projects

🔌 Installation

# NPM
npm install --save-dev typelab

# BUN
bun add -d typelab

📔 Docs

Showcases

Here is an example for some types from each categories.

Aliases

• Primitive

  const value1: Primitive = ""; // valid
  const value2: Primitive = {}; // invalid

• Nullable

  const example: Nullable<string> = null; // valid
  const example2: Nullable<string> = undefined; // invalid

• Undefinable

  const example: Undefinable<string> = undefined; // valid
  const example2: Undefinable<string> = null; // invalid

Assertions

• IsExtends

  type Extends = IsExtends<'', string>; // true
  type NotExtends = IsExtends<string, ''>; // false

• IsEqual

  type Equal = IsEqual<string, string>; // true
  type NotEqual = IsEqual<string, ''>; // false

• IsAny

  type Valid = IsAny<any>; // true
  type Invalid = IsAny<string>; // false

Conditions

• IfExtends

  type Yes = IfExtends<'', string, 'yes', 'no'>; // 'yes'
  type No = IfExtends<string, '', 'yes', 'no'>; // 'no'
  type YesOrNo = IfExtends<string | number, string, 'yes', 'no'>; // 'yes' | 'no'

• IfEqual

  type Yes = IfEqual<string, string, 'yes', 'no'>; // 'yes'
  type No = IfEqual<string, number, 'yes', 'no'>; // 'no'

• IfAny

  type Yes = IfAny<any, 'yes', 'no'>; // 'yes'
  type No = IfAny<string, 'yes', 'no'>; // 'no'

Utils

• FunctionCallbackify

  // (a: string, callback: (error: unknown, result: string) => void) => void
  type Callbackified = FunctionCallbackify<(a: string) => Promise<string>>;

• FunctionPromisify

  // Callback-style function:
  // (a: string) => Promise<string>
  type Promisified = FunctionPromisify<(a: string, callback: (error: Error, result: string) => void) => void>;
  
  // Regular function:
  // (a: string) => Promise<string>
  type PromisifiedFn = FunctionPromisify<(a: string) => string>;

• ObjectAssign

  // { a: string; b: string; c: boolean }
  type Assign1 = ObjectAssign<{ a: string; b: number }, { b: string; c: boolean }>;
  
  // { a: string; 0: string }
  type Assign2 = ObjectAssign<{ a: string }, [string]>;
  
  // { [x: number]: string, a: string }
  type Assign3 = ObjectAssign<{ a: string }, string[]>;
  
  // [number, number]
  type Assign4 = ObjectAssign<[string], [number, number]>;
  
  // (string | number)[]
  type Assign5 = ObjectAssign<string[], [number, number]>;
  
  // (string | number)[]
  type Assign6 = ObjectAssign<string[], number[]>;
  
  // [number, string]
  type Assign7 = ObjectAssign<[string], { 0: number; 1: string }>;
  
  // (string | number)[]
  type Assign8 = ObjectAssign<[number], 'str'>;
  
  // { [x: number]: string, a: string }
  type Assign9 = ObjectAssign<{a: string}, 'str'>;

All Available Types

A complete reference for all available reusable types.

Aliases

• Arrays
  Array · Arr · List · ReadonlyArray · ReadonlyArr · ReadonlyList · WritableArray · WritableArr · WritableList

• Tuples
  ReadonlyTuple · Tuple · WritableTuple

• Functions
  AsyncFn · AsyncFunction · Fn · Function · NewableFn · NewableFunction

• Objects
  ObjectArrayLike · ObjectEmpty · ObjectGeneric

• Misc
  Any · Async · Class · Falsy · Infinity · NegativeInfinity · NonNullish · Nullish · Nullable · Primitive · PositiveInfinity · Undefinable · Void

Assertions

• Arrays
  IsArray · IsArrayReadonly · IsArrayWritable

• Tuples
  IsTuple · IsTupleReadonly · IsTupleWritable

• Functions
  IsAsyncFunction · IsFunction · IsNewableFunction

• Objects
  IsObject · IsObjectArrayLike · IsObjectEmpty · IsObjectLiteral · IsOptionalProperty · IsRequiredProperty

• Primitives
  IsBigInt · IsBoolean · IsFalse · IsNull · IsNumber · IsNumberDecimal · IsNumberInteger · IsNumberLiteral · IsPrimitive · IsString · IsStringLiteral · IsSymbol · IsTrue · IsUndefined

• Comparisons
  IsAssignable · IsAssignableEitherWay · IsAssignableMutually · IsEqual · IsExtends · IsNotAssignable · IsNotAssignableEitherWay · IsNotAssignableMutually · IsNotEqual · IsNotExtends

• Misc
  IsAny · IsClass · IsFalsy · IsIntersected · IsNever · IsNonNullish · IsNullish · IsPositive · IsPropertyKey · IsPromise · IsTruthy · IsUnion · IsUndefinable · IsUnknown · IsVoid

Conditions

• Arrays
  IfArray · IfArrayReadonly · IfArrayWritable

• Tuples
  IfTuple · IfTupleReadonly · IfTupleWritable

• Functions
  IfAsyncFunction · IfFunction · IfNewableFunction

• Objects
  IfObject · IfObjectArrayLike · IfObjectEmpty · IfObjectLiteral · IfOptionalProperty · IfRequiredProperty

• Primitives
  IfBigInt · IfBoolean · IfFalse · IfNull · IfNumber · IfNumberDecimal · IfNumberInteger · IfNumberLiteral · IfPrimitive · IfString · IfStringLiteral · IfSymbol · IfTrue · IfUndefined

• Comparisons
  IfAssignable · IfAssignableEitherWay · IfAssignableMutually · IfEqual · IfExtends · IfNotAssignable · IfNotAssignableEitherWay · IfNotAssignableMutually · IfNotEqual · IfNotExtends

• Misc
  IfAny · IfClass · IfFalsy · IfIntersected · IfNever · IfNonNullish · IfNullish · IfPositive · IfPropertyKey · IfPromise · IfTruthy · IfUnion · IfUndefinable · IfUnknown · IfVoid

Utils

• Arrays
  ArrayLength · ArrayElements · ArrayValues · ArrayIndexes · ArrayAt · ArrayFirst · ArrayLast · ArrayConcat · ArrayPush · ArrayPop · ArrayUnshift · ArrayShift · ArrayFlat · ArrayTake · ArraySkip · ArrayRequired · ArrayPartial · ArrayRequiredIndexes · ArrayOptionalIndexes · ArrayRequiredElements · ArrayOptionalElements · ArrayRequiredValues · ArrayOptionalValues · ArrayOmitRequired · ArrayOmitOptional · ArrayToObject · ArrayAssign · ArrayOverwrite · ArrayMerge · ArrayUnionize

• Objects
  ObjectPick · ObjectRequired · ObjectPartial · ObjectRequiredKeys · ObjectOptionalKeys · ObjectOmitRequired · ObjectOmitOptional · ObjectReadonly · ObjectWritable · ObjectPath · ObjectPathValue · ObjectToTuple · ObjectAssign · ObjectOverwrite · ObjectMerge · ObjectUnionize

• Functions
  FunctionAssign · FnAssign · FunctionOverwrite · FnOverwrite · FunctionMerge · FnMerge · FunctionPromisify · FnPromisify · FunctionCallbackify · FnCallbackify

• Unions
  UnionToIntersection · UnionLast · UnionPop · UnionIntersection · UnionExclusive · UnionToTuple

• Parsing
  ParseInt · ParseIntNegative · ParseIntPositive · ParseFloat · ParseFloatNegative · ParseFloatPositive · ParseBigInt · ParseBigIntNegative · ParseBigIntPositive · ParseString · ParseBoolean · ParseObject

• Maths
  Increment · Decrement

• Misc
  Brand · Detailed · ExcludeNullish · ExcludeNull · ExcludeUndefined · ExtractArray · ExtractPromise · ExtractParams · ExtractReturn · KeyOf · Mapped · PropValue · Toggle · ValueOf

⛏️ Built Using

• Typescript
  Strongly typed programming language that builds on JavaScript.
• Bun
  All-in-one JavaScript runtime & toolkit designed for speed, complete with a bundler, test runner, and Node.js-compatible package manager.

📄 License

The code in this project is released under the MIT License.