generators.js

Array.prototype.toIterator = function*() {
  for (var i = 0, l = this.length; i < l; i++) {
    yield this[i]
  }  
}

Object.prototype.map = function*(lambda) {
  for (var value of this) {
    yield lambda(value)
  }  
}

Object.prototype.take = function*(n) {
  for (var i = 0; i < n; i++) {
    var value = this.next().value
    if (typeof value == 'undefined') break
    yield value
  }
}

Object.prototype.toArray = function(n) {
  var list = []
  for (var item of this) {
    list.push(item)
  }
  return list
}

var array = [0, 1, 2, 3, 4, 5, 6, 7]
var addOne = function(v) {
  return v + 1
}

var result = array.toIterator().map(addOne).take(3).toArray()
console.log(result)