Lazy Stream in JS

var Id = v => ({v: v,map: f => Id(f(v)) });


 var CoFreeF = (a, next) => ({
   a: a,
   next: next,
   extract: () => a,
   map: g => CoFreeF(g(a), () => next().map(x=>x.map(g))),
 });
 
 var f = n => CoFreeF(n + 1, () => Id(f(n + 1)));

 var stream = f(0);
 console.log(stream)

 var x = stream.next().v.next().v.map(x => x * 2).next().v;
 console.log(x);