Isn't this beautiful?

delay.js

var $=(f,c,t,r)=>(r=(t=t||f()).next()).done?c&&c(r.value):setTimeout(()=>$(f,c,t),r.value);

$(function *() {
	console.log(1);
	yield 1000;
	console.log(2);
	yield 1000;
	console.log(3);
	yield 1000;
	return 4;
}, function (res) {
	console.log('result = ', res);
});