MultipleInheritance.js

// Taken from https://stackoverflow.com/questions/9163341/multiple-inheritance-prototypes-in-javascript

function getDesc (obj, prop) {
  let desc = Object.getOwnPropertyDescriptor(obj, prop);
  return desc || (obj=Object.getPrototypeOf(obj) ? getDesc(obj, prop) : void 0);
}

function multiInherit (...protos) {
  return Object.create(new Proxy(Object.create(null), {
    has: (target, prop) => protos.some(obj => prop in obj),
    get (target, prop, receiver) {
      let obj = protos.find(obj => prop in obj);
      return obj ? Reflect.get(obj, prop, receiver) : void 0;
    },
    set (target, prop, value, receiver) {
      let obj = protos.find(obj => prop in obj);
      return Reflect.set(obj || Object.create(null), prop, value, receiver);
    },
    *enumerate (target) { yield* this.ownKeys(target); },
    ownKeys(target) {
      let hash = Object.create(null);
      for(let obj of protos) for(let p in obj) if(!hash[p]) hash[p] = true;
      return Object.getOwnPropertyNames(hash);
    },
    getOwnPropertyDescriptor(target, prop) {
      let obj = protos.find(obj => prop in obj);
      let desc = obj ? getDesc(obj, prop) : void 0;
      if(desc) desc.configurable = true;
      return desc;
    },
    preventExtensions: (target) => false,
    defineProperty: (target, prop, desc) => false,
  }));
}