generator2.js

function *fibonacci(){
	let first = 1;
	let second = 1;
	while (true){  
		let current = second;
		second = first;
		first = first + current;
		yield current;
	}
}

let fib = fibonacci();

console.log(fib.next()) // 1
console.log(fib.next()) // 1
console.log(fib.next()) // 2
console.log(fib.next()) // 3
console.log(fib.next()) // 5
console.log(fib.next()) // 8 etc.