generators-es6.js

const base = 5;

function *sum(num) {
	let result = num + base;
	
	num = yield(result);
	return (result + num);
}

let it = sum(16);
console.log(it.next()); // {"value":21,"done":false} 
console.log(it.next(12)); // {"value":33,"done":true}