AsyncGetSet.js

const o = {
	note: 'default note'
};

Object.defineProperty(o, 'letter', {
	get: async function () {
		return this.note;
	},
	set: async function (value) {
		await new Promise((resolve) => {
			setTimeout(() => {
				o.note = value;
				resolve();
			}, 100);
		});
	}
});

Object.defineProperty(o, 'as_async_value', {
	async set (value) {
		if (value instanceof Function) {
			o.note = await value();
			return;
		}
		o.note = value;
	}
});

(async function () {
	debugger;
	console.log('o.letter : ', o.letter);
	console.log('await o.letter : ', await o.letter);
	o.letter = 123;
	console.log('o.note : ', o.note);
	await (o.letter = 123);
	console.log('awaited o.letter : ', await o.letter);
	console.log('o.letter = 321 : ', o.letter = 321)
	console.log('o.note : ', o.note);
	console.log('await (o.letter = "awaited letter"): ', await (o.letter = 'awaited letter'));
	console.log('o.note : ', o.note);
	console.log('await o.letter : ', await o.letter);
	setTimeout(() => {
		console.log('o.note : ', o.note);
	}, 200);
	
	setTimeout(async () => {
		console.log('as_async_value_set await', await (o.as_async_value = async () => { return 'as_async_value await'}));
		console.log('as_async_value_set await o.note : ', o.note);
	}, 300);

	setTimeout(async () => {
		console.log('as_async_value_set', o.as_async_value = async () => { return 'as_async_value'});
		console.log('as_async_value_set o.note : ', o.note);
	}, 350);
	
	setTimeout(() => {
		console.log('as_async_value_set after timeout o.note : ', o.note);
	}, 400);

	setTimeout(async () => {
		console.log('as_async_value_set non async', o.as_async_value = 'non_async_as_async_value_value');
		console.log('as_async_value_set non async o.note : ', o.note);
	}, 500);


})();