lazySequences.js

"use strict"

// Iterator with generator
let fibonacci =
{
	[Symbol.iterator]: function*()
	{
    	let pre = 0, cur = 1
    	
    	while(true)
    	{
      		let temp = pre
      		pre = cur
      		cur += temp
      		yield cur
    	}
  	}
}

for(let n of fibonacci)
{
	if(n > 1000)
	{
		break
	}

	console.log(n)
}

// Generator function
let fibonacci = function*()
{
	let pre = 0, cur = 1
	
	while(true)
	{
  		let temp = pre
  		pre = cur
  		cur += temp
  		yield cur
	}
}

let temp = fibonacci()

while(true)
{
	let next = temp.next()

	if(next.done || next.value > 1000)
	{
		break
	}

	else
	{
		console.log(next.value)
	}
}