function choose(arr, size) {
  var allResult = [];

  (function (arr, size, result) {
    var arrLen = arr.length;
    if (size > arrLen) {
      return;
    }
    if (size == arrLen) {
      allResult.push([].concat(result, arr))
    } else {
      for (var i = 0; i < arrLen; i++) {
        var newResult = [].concat(result);
        newResult.push(arr[i]);

        if (size == 1) {
          allResult.push(newResult);
        } else {
          var newArr = [].concat(arr);
          newArr.splice(0, i + 　1);
          arguments.callee(newArr, size - 1, newResult);
        }
      }
    }
  })(arr, size, []);

  return allResult;
}