Flumix

A lightweight, type-safe mixin library for TypeScript that enables composable class inheritance with a fluent API.

Installation

npm install flumix

Features

• 🔒 Type-safe: Full TypeScript support with proper type inference
• 🧩 Composable: Easily combine multiple mixins with a fluent API
• 🪶 Lightweight: Zero dependencies, minimal footprint
• 🔧 Flexible: Works with any class hierarchy

Usage

Basic Example

import { mix } from "flumix";

// Base class
class Animal {
  isAlive = true;
}

// Mixin functions
function Swimming(Base) {
  return class extends Base {
    swim() {
      return "Swimming!";
    }
  };
}

function Flying(Base) {
  return class extends Base {
    fly() {
      return "Flying!";
    }
  };
}

// Create a class that combines Animal with Swimming and Flying abilities
const Duck = mix(Animal).with(Swimming).with(Flying).build();

// Use the composed class
const duck = new Duck();
console.log(duck.isAlive); // true
console.log(duck.swim()); // "Swimming!"
console.log(duck.fly()); // "Flying!"

With Constructor Parameters

// Base class with constructor
class Person {
  name: string;

  constructor(name: string) {
    this.name = name;
  }
}

// Mixin with options
function Aged(Base, defaultAge: number) {
  return class extends Base {
    age: number;

    constructor(...args: any[]) {
      super(...args);
      this.age = defaultAge;
    }

    getAge() {
      return this.age;
    }
  };
}

// Create a composed class with parameters
const AgedPerson = mix(Person).with(Aged, 30).build();

const person = new AgedPerson("John");
console.log(person.name); // "John"
console.log(person.getAge()); // 30

API

mix(BaseClass) / extend(BaseClass)

Both functions are identical and create a new MixinBuilder for the given base class.

MixinBuilder.with(mixinFn, ...options)

Applies a mixin function to the current base class, optionally with additional parameters.

MixinBuilder.build()

Finalizes the mixin chain and returns the resulting class.

Compatibility

• Works with ES6+ environments
• Full TypeScript support (4.0+)

License

MIT © José F. Romaniello