ExtendableString

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

📃 Table of Contents

• Features
• Usage
• API
  • constructor()
  • value
  • toString()
• Examples
• Changelog
• Support
• License
• Related
• Author

🤖 Features

• 🚀 Instantly applies custom string transformations on creation
• 🔄 Updates value with transformation applied automatically
• 🛡️ Validates transformation function before use
• 🧩 Designed for easy extension via sub-classing
• 📦 Encapsulates logic with private fields for safety
• 📝 Provides clean string output through the toString() method
• ⚡ Ensures consistent transformed state at all times

🕵🏼 Usage

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

pnpm add @igorskyflyer/extendable-string

yarn add @igorskyflyer/extendable-string

npm i @igorskyflyer/extendable-string

🤹🏼 API

💡 TIP

First Steps

Do NOT instantiate a new object from the ExtendableString class, extend it instead.

constructor(raw, transformFn)

Creates an ExtendableString instance.

raw - The string input to transform.

transformFn - The transformation function to apply to the string.

Will throw an error if the transformation function is not supplied.

value: string

Gets the transformed string or sets a new value that will be transformed automatically.

toString(): string

Gets the transformed string value.

Returns the transformed string.

🗒️ Examples

UpperCaseString.ts

import { ExtendableString } from '@igorskyflyer/extendable-string'

export class UpperCaseString extends ExtendableString {
  constructor(value: string) {
    super(value, (str) => str.toUpperCase())
  }
}

example.ts

import { UpperCaseString } from './UpperCaseString.js'

const test = new UpperCaseString('aaaa')
console.log(test.value) // Outputs 'AAAA'

const example = new UpperCaseString('aaaa')
example.value = 'hello'
console.log(test.value) // Outputs 'HELLO'

📝 Changelog

📑 The changelog is available here, CHANGELOG.md.

🪪 License

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

💖 Support

I work hard for every project, including this one and your support means a lot to me!
Consider buying me a coffee. ☕



Thank you for supporting my efforts! 🙏😊

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👨🏻‍💻 Author

Created by Igor Dimitrijević (@igorskyflyer).

📒 Changelog

of @igorskyflyer/extendable-string

v2.1.0 (04-Sep-2025)

• 💻 dev: upgrade Node to >= v22
• 💻 dev: upgrade dependencies

v2.0.0 (29-Jul-2024)

• ❌ BREAKING: migrate to Node v20 and ESM-only
• ✅ fix: minor improvements