JavaScript infinite streams

infinite-streams.js

const stream = (value, next = null) => ({
  map: function(f) {
    return stream(f(value), next ? next.map(f) : null)
  },

  filter: function(pred) {
    if (pred(value)) {
      return stream(value, next ? next.filter(pred) : null)
    } else {
      return next ? next.filter(pred) : emptyStream
    }
  },
  value,
  next
})

const emptyStream = {
  map: function() {
    return this
  },

  filter: function() {
    return this
  }
}

const stream1 = stream(1, stream(2, stream(3, emptyStream)))
const mappedStream = stream1.map(x => x.toString())
const filteredStream = stream1.filter(x => x > 1)
console.log(mappedStream) // { value: '1', next: {...}, map: [Function], next: { map: [Function], next: { map: [Function], next: [Object] } } }
console.log(filteredStream) // { value: 2, next: {...}, map: [Function], next: { map: [Function], next: [Object] } }