📃 Table of Contents

• Features
• API
  • KeysOf<Type>
  • TypeOfValues<Type>
  • MethodsOf<Type>
  • PropertiesOf<Type>
  • DeepPartial<Type>
  • Promisable<Type>
  • EnumKeys<Type, KeyType>
  • Func<Args, FnReturn>
  • Callback<Args, FnReturn>
  • TrimLeft<Input>
  • TrimRight<Input>
  • Trim<Input>
  • IsGeneric<Type>
  • MethodSignature<Type, Method>
  • Override<Type, Changes>
  • HasOverlap<FirstType, SecondType>
  • Extend<Type, Changes>
  • MethodName<Type, Method>
• Usage
• API
• Examples
• Changelog
• Support
• License
• Related
• Author

🤖 Features

• 🗝 Get all keys of a type with KeysOf
• 📦 Extract all value types from top-level properties via TypeOfValues
• 🔍 Identify only method keys using MethodsOf
• 🧾 Identify only property keys using PropertiesOf
• 🌿 Make every property (nested too) optional with DeepPartial
• ⏳ Accept sync or async values using Promisable
• 🎯 Find keys whose values match a specific type via EnumKeys
• 🛠 Define generic function signatures with Func or Callback
• ✂ Remove leading/trailing whitespace in string types with TrimLeft, TrimRight, Trim
• ❓ Detect generic types using IsGeneric
• 📜 Get a method’s exact signature with MethodSignature
• 📝 Override existing keys with new types via Override
• 🚫 Prevent extending with overlapping keys using Extend
• 🔑 Validate a method exists and return its name with MethodName

🕵🏼 Usage

Install it by executing any of the following, depending on your preferred package manager:

pnpm add @igorskyflyer/common-types

yarn add @igorskyflyer/common-types

npm i @igorskyflyer/common-types

🤹🏼 API

KeysOf<Type>

Extracts all keys from the type Type.

💡 TIP

CAN be used with generics as well.

example.ts

type ArrayKeys = KeysOf<Array<string>> // 'at' | 'concat' | 'copyWithin', etc.

TypeOfValues<Type>

Extracts all value types of the type Type. Works with top-level properties only.

IPerson.ts

interface IPerson {
  firstName: string
  lastName: string
  zip: number
  isMember: boolean
}

example.ts

type ValueTypes = TypeOfValues<IPerson> // string | number | boolean

MethodsOf<Type>

Extracts all methods from the type Type.

🛑 CAUTION

Can NOT be used with generics.

example.ts

type NumberMethods = MethodsOf<Number> // 'toString' | 'toFixed' | 'toExponential' | 'toPrecision' | 'valueOf' | 'toLocaleString'

PropertiesOf<Type>

Extracts all properties from the type Type.

🛑 CAUTION

Can NOT be used with generics.

example.ts

type StringProperties = PropertiesOf<String> // 'length'

DeepPartial<Type>

Constructs a type with all top-level and nested properties of the type Type set to optional.

💡 TIP

See also TypeScript's built-in utility type Partial<Type> .

IPerson.ts

interface IPerson {
  name: string
  address: {
    city: string
    zip: number
  }
}

example.ts

type PersonOptional = DeepPartial<IPerson>

/**
 * PersonOptional:
 *  {
 *    name?: string
 *    address?: {
 *      city?: string
 *      zip?: number
 *    }
 *  }
 */

Promisable<Type>

Provides a convenient way to allow flexibility in handling values that could either be immediate or asynchronously resolved.

example.ts

const immediateValue: number = 42
const promiseValue: Promisable<number> = Promise.resolve(42)

async function handleValue(value: Promisable<number>) {
  const result = await processValue(value)
  console.log(result) // Will log the number 42, whether value was a direct number or a Promise resolving to 42
}

handleValue(immediateValue)
handleValue(promiseValue)

EnumKeys<Type, KeyType>

Extracts all keys from the Type that are of the type KeyType.

IConfig

interface IConfig {
  apiUrl: string
  timeout: number
  isEnabled: boolean
  retryAttempts: number
}

example.ts

type ConfigNumbers = EnumKeys<IConfig, number> // 'timeout' | 'retryAttempts'

Func<Args, FnReturn>

Constructs a generic Function-like type with the arguments of type Args and the return value of type FnReturn.

example.ts

function process(items: number[], callback: Func<number, boolean>): boolean {
  // shortened for brevity
  // do NOT access your Array immediately :)
  for (let i = 0; i < items.length; i++) {
    if (callback(items[i])) {
      return true
    }
  }

  return false
}

process([1, 1, 8, 1], (item) => {
  if (item % 2 === 0) {
    return true
  }

  return false
}) // returns true

Callback<Args, FnReturn>

Alias of Func<Args, FnReturn>.

TrimLeft<Input>

Recursively removes all leading whitespace from the String type Input.

example.ts

type Id = '    ID'
type ProperId = TrimLeft<Id>

const id: ProperId = '   ID' // ERROR: does NOT accept leading whitespace

TrimRight<Input>

Recursively removes all trailing whitespace from the String type Input.

example.ts

type Id = 'ID     '
type ProperId = TrimRight<Id>

const id: ProperId = 'ID    ' // ERROR: does NOT accept leading whitespace

Trim<Input>

Recursively removes all leading and trailing whitespace from the String type Input.

example.ts

type Id = '    ID     '
type ProperId = Trim<Id>

const id: ProperId = '   ID    ' // ERROR: does NOT accept leading nor trailing whitespace

💡 TIP

A very cool usage of the Trim<Input> type is implemented in the magic-querySelector project.

IsGeneric<Type>

Returns a Boolean whether the type Type is a generic.

example.ts

type ArrayIsGeneric = IsGeneric<Array<string>> // true
type NumberIsGeneric = IsGeneric<number> // false

MethodSignature<Type, Method>

Gets the method signature Method of the type Type.

example.ts

type NumberToFixedMethod = MethodSignature<Number, 'toFixed'> // expects (fractionDigits?: number) => string

Override<Type, Changes>

Overrides the type Type with the new type of Changes.

IPerson

interface IPerson {
  name: string
  children: boolean
}

example.ts

const person: IPerson = {
  name:'John Doe',
  children: true
}

type NewPerson = Override<IPerson, { children: number }> //only accepts existing keys

const newPerson: NewPerson = {
  name:'John Doe',
  children: 2
}

HasOverlap<FirstType, SecondType>

Checks whether the types FirstType and SecondType overlap, i.e. have the same keys.

⚠️ WARNING

It only checks the key names, NOT their TYPES!

IPerson

interface IPerson {
  name: string
  children: boolean
}

example.ts

type PersonOverlap = HasOverlap<
  IPerson,
  {
    name: string
    children: boolean
  }
> // returns true

Extend<Type, Changes>

Extends the type Type with the new type of Changes with only non-existent keys in type Type.

IPerson

interface IPerson {
  name: string
  children: number
}

example.ts

type NewPerson = Extend<IPerson, { name: string }> //only accepts non-existing keys
// will return `never` here
const newPerson: NewPerson = {
  name: 'John Doe',
  children: 2
} // will error

type NewestPerson = Extend<IPerson, { profession: string }> //only accepts non-existing keys
const newestPerson: NewestPerson = {
  name: 'John Doe',
  children: 2,
  profession: 'Developer'
} // will NOT error

MethodName<Type, Method>

Checks for the existence of the method Method in the type of Type and returns it if found.

example.ts

type NumberToFixedMethod = MethodName<Number, 'toFixed'> // toFixed

🗒️ Examples

utils.ts

import type { Callback } from '@igorskyflyer/common-types'

function process(
  items: number[],
  callback: Callback<number, boolean>
): boolean {
  // shortened for brevity
  // do NOT access your Array immediately :)
  for (let i = 0; i < items.length; i++) {
    if (callback(items[i])) {
      return true
    }
  }

  return false
}

const result = process([1, 1, 8, 1], (item) => {
  if (item % 2 === 0) {
    return true
  }

  return false
}) // returns true

console.log(result)

📝 Changelog

📑 The changelog is available here, CHANGELOG.md.

🪪 License

Licensed under the MIT license which is available here, MIT license.

💖 Support

🧬 Related

@igorskyflyer/windev

🍃 Provides ways of checking whether a path is a legacy Windows device. 💾

@igorskyflyer/magic-queryselector

🪄 A TypeScript-types patch for querySelector/querySelectorAll, make them return types you expect them to! 🔮

@igorskyflyer/jmap

🕶️ Reads a JSON file into a Map. 🌻

@igorskyflyer/clone

🧬 A lightweight JavaScript utility allowing deep copy-by-value of nested objects, arrays and arrays of objects. 🪁

@igorskyflyer/extendable-string

🦀 ExtendableString allows you to create strings on steroids that have custom transformations applied to them, unlike common, plain strings.. 🪀

👨🏻‍💻 Author

Created by Igor Dimitrijević (@igorskyflyer).