js函数 字符串->二维数组,该怎么解决

$ar_name =".血液病.白血病.地中海贫血.颈椎病.腰椎间盘突出.关节炎" ;

array(59) {
  [0]=>
  array(1) {
    [0]=>
    string(4) "血液病"
  }
  [1]=>
  array(1) {
    [0]=>
    string(6) "白血病"
  }
  [2]=>
  array(1) {
    [0]=>
    string(12) "地中海贫血"
  }
  [3]=>
  array(1) {
    [0]=>
    string(4) "颈椎病"
  }
  [4]=>
  array(1) {
    [0]=>
    string(6) "腰椎间盘突出"
  }
  [5]=>
  array(1) {
    [0]=>
    string(10) "关节炎"
  }
}

var str = '.血液病.白血病.地中海贫血.颈椎病.腰椎间盘突出.关节炎';
var ar = str.substring(1).split('.');
var result = [];
for (x in ar) result.push(new Array(ar[x]));