FancyObject Library

A TypeScript utility library for creating objects with enhanced behaviors, including conditional properties, multi-key mappings, and default fallback values.

Table of Contents

• FancyObject Library
  • Table of Contents
  • Installation
  • Features
  • Usage
    • Creating a Fancy Object
    • Using otherwise()
    • Adding Conditional Properties with addIf
    • Assigning Multiple Keys with multiKey
    • Accessing Properties Safely with access
  • Complete Example
  • API Reference
    • fancyObject
    • otherwise
    • addIf
    • multiKey
    • access
  • Running Tests
  • Contributing
  • License

Installation

You can install the library via npm:

npm install fancy-object

Or using yarn:

yarn add fancy-object

Or using pnpm:

pnpm add fancy-object

Features

• Fancy Objects: Create objects that return a default value when accessing undefined properties.
• Conditional Properties: Conditionally add properties to objects based on a boolean condition.
• Multi-Key Mappings: Assign the same value to multiple keys within an object.
• TypeScript Support: Fully typed with type inference for an enhanced developer experience.

Usage

Creating a Fancy Object

The fancyObject function wraps a plain object and enhances its behavior. If you try to access a property that doesn't exist and an otherwise value is defined, it will return that default value.

import { fancyObject } from 'fancy-object';

const obj = fancyObject({
  key1: 'value1',
  key2: 'value2',
});

console.log(obj.key1); // Output: 'value1'
console.log(obj.nonExistentKey); // Output: undefined

Using otherwise()

The otherwise() function allows you to define a default value for any undefined properties accessed on the object.

import { fancyObject, otherwise } from 'fancy-object';

const obj = fancyObject({
  key1: 'value1',
  [otherwise()]: 'Default value when key is not found',
});

console.log(obj.key1); // Output: 'value1'
console.log(obj.unknownKey); // Output: 'Default value when key is not found'

Adding Conditional Properties with addIf

Use addIf to conditionally add properties to your object based on a boolean condition.

import { fancyObject, addIf } from 'fancy-object';

const isAdmin = true;

const obj = fancyObject({
  key1: 'value1',
  ...addIf(isAdmin, 'adminPanel', 'Admin Access'),
});

console.log(obj.adminPanel); // Output: 'Admin Access' if isAdmin is true

Assigning Multiple Keys with multiKey

The multiKey function allows you to assign the same value to multiple keys.

import { fancyObject, multiKey } from 'fancy-object';

const obj = fancyObject({
  ...multiKey(['key1', 'key2'], 'shared value'),
});

console.log(obj.key1); // Output: 'shared value'
console.log(obj.key2); // Output: 'shared value'

Accessing Properties Safely with access

The access function provides a type-safe way to access properties of an object.

import { fancyObject, access } from 'fancy-object';

const obj = fancyObject({
  key1: 'value1',
});

console.log(access(obj, 'key1')); // Output: 'value1'

Complete Example

Here's how you can combine these utilities:

import { fancyObject, addIf, multiKey, otherwise } from 'fancy-object';

const obj = fancyObject({
  key1: 'value1',
  ...addIf(true, 'key2', 'value2'),
  ...addIf(false, 'key3', 'value3'), // This key will not be added
  ...multiKey(['admin', 'user'], 'multi-user value'),
  [otherwise()]: 'Default value when key is not found',
});

console.log(obj.key1); // Output: 'value1'
console.log(obj.key2); // Output: 'value2'
console.log(obj.key3); // Output: 'Default value when key is not found'
console.log(obj.admin); // Output: 'multi-user value'
console.log(obj.user); // Output: 'multi-user value'
console.log(obj.unknownKey); // Output: 'Default value when key is not found'

API Reference

fancyObject

function fancyObject<T extends Record<PropertyKey, any>>(POJO: T): FancyObject<T>

• Description: Wraps a plain object to provide enhanced behaviors, such as returning a default value for undefined properties if an otherwise value is defined.
• Parameters:
  • POJO: The plain object to enhance.
• Returns: An enhanced object with the same properties as POJO, and potentially with an index signature if an otherwise value is provided.

otherwise

function otherwise(): symbol

• Description: Returns a special symbol used as a key to define a default value in a fancy object.
• Usage:

const obj = fancyObject({
  key1: 'value1',
  [otherwise()]: 'Default value',
});

addIf

function addIf<C extends boolean, K extends ObjectKey, V>(
  condition: C,
  key: K,
  value: V
): C extends true ? Record<K, V> : {}

• Description: Conditionally adds a property to an object based on a boolean condition.
• Parameters:
  • condition: A boolean determining whether to add the property.
  • key: The key of the property to add.
  • value: The value of the property to add.
• Returns: An object with the property if condition is true, or an empty object if false.

multiKey

function multiKey<K extends ObjectKey[], V>(keys: [...K], value: V): Record<K[number], V>

• Description: Assigns the same value to multiple keys in an object.
• Parameters:
  • keys: An array of keys.
  • value: The value to assign to each key.
• Returns: An object mapping each key to the given value.

access

function access<O extends object>(fancyObject: O, key: keyof O): O[keyof O]

• Description: Safely accesses a property in an object, with TypeScript type checking.
• Parameters:
  • fancyObject: The object to access.
  • key: The key of the property to access.
• Returns: The value of the property at the given key.

Running Tests

The library includes a comprehensive test suite. To run the tests, use:

npm test

Ensure you have all the dependencies installed and that you're in the root directory of the project.

Contributing

Contributions are welcome! If you have suggestions or find bugs, please open an issue or submit a pull request.

1. Fork the repository.

2. Create a new branch:

   git checkout -b feature/your-feature-name

3. Commit your changes:

   git commit -am 'Add some feature'

4. Push to the branch:

   git push origin feature/your-feature-name

5. Open a pull request.

Please make sure to update tests as appropriate.

License

This project is licensed under the MIT License.