適当な非同期処理(Promise)

async function waitNsecond(n){
	return new Promise(function(resolve,reject){
		setTimeout(resolve,1000);
	});
}

type1

// set super class
var SUPER=Array;
// define async constructor
async function constructor(...args){
//	console.log(this);
	SUPER.call(this);
	this.push(...args);
	await waitNsecond(1);
}
// define async generate class
function myAsyncClass(...args){
	if(new.target){
		return new Promise(async function(resolve,reject){
			let instance=Object.create(myAsyncClass.prototype);
			await constructor.call(instance,...args);
			resolve(instance);
		});
	}
}
// set prototype
myAsyncClass.prototype=Object.create(SUPER.prototype);
Object.defineProperty(myAsyncClass.prototype, 'constructor', { value: myAsyncClass, enumerable: false, writable: true });
// define method
myAsyncClass.prototype.printAll=function(){ console.log(this.join()); };

type2

class myAsyncClass extends Array {
	constructor(...args){
		super();
		let instance=this;
		return new Promise(async function(resolve,reject){
			instance.push(...args);
			await waitNsecond(1);
			resolve(instance);
		});
	};
	printAll(){
		console.log(this.join());
	};
}

結果

let instance=await new myAsyncClass(5,6,7,8,9);
instance.constructor===myAsyncClass;
instance.printAll();	// 5,6,7,8,9

だいぶ雑だけど基本はこんな感じでいける。かなぁ...