Simulating Multiple Inheritance

An object can have only ONE prototype. But what if a class needs behavior from several sources? Enter Mixins — plain objects whose methods are copied onto a class prototype.

const Serializable = {
  serialize() { return JSON.stringify(this); }
};

const Loggable = {
  log(message) { console.log(`[${this.constructor.name}] ${message}`); }
};

class User {
  constructor(name) { this.name = name; }
}

// Mix both toolboxes into User
Object.assign(User.prototype, Serializable, Loggable);

const user = new User('Alice');
user.log('logged in');         // [User] logged in
console.log(user.serialize()); // {"name":"Alice"}