code: function getRange(start, stop, fn, step) {
      var arr = [], i = parseInt(start), down = step < 0;
      while((!down && i <= stop) || (down && i >= stop)) {
        arr.push(i);
        if(fn) fn.call(this, i);
        i += step || 1;
      }
      return arr;
    }
docs: Number helpers