for (var i of (1).upto(5)) { ... }

number-upto.js

Number.prototype.upto = function upto(end) {
  var start = this;
  function NumberIterator() {
    this.current = start;
  }
  NumberIterator.prototype.next = function next() {
    if (this.current > end) {
      throw StopIteration;
    } else {
      return this.current++;
    }
  };
  return {__iterator__: function() { return new NumberIterator() }};
};