如何选择字符串中的最后一个数字？

Question

我有一个这样的字符串：

var str = "this is test 
      1. this is test 
      2. this is test 
       3. this is test 
      this is test 
      1. this test 
        2. this is test"; 

我想2。

又如：

var str = "this is test 
      1. this is test 
      2. this is test 
       3. this is test 
      this is test 
      1. this test 
        2. this is test 
      this is test"; 

我想2。

又如：

var str = "this is test 
      1. this is test 
      2. this is test 
       3. this is test 
      this is test 
      1. this test 
        2. this is test 

      this is test"; 

我想null，因为连续两个\n中断该序列。

---

正如你看到的，我想最后的数字是列表样式。像这样：

{spaces in here doesn't matter}{any digit}{dot}{every thing in here til end of line} 

我该怎么做？

Answer 1

尝试这种模式

^[\s\S]*(?:^|\r?\n)\s+(\d+)(?![\s\S]*(\r?\n){2}) 

Demo

一个强制性点的数量使用后什么

^[\s\S]*(?:^|\r?\n)\s+(\d+)\.(?![\s\S]*(\r?\n){2}) 

解释：

^[\s\S]*     # from the beginning "^" consume everything 
(?:^|\r?\n)     # if not first line then followed by a newline 
\s*       # followed by white spaces 
(\d+)      # capturing group to get your number 
(?!       # a negative look-ahead 
    [\s\S]*(\r?\n){2}  # anything followed by {2} new lines 
)       # end of negative look-ahead 

Answer 2

这应该是那么容易，因为只是运行

(string.match(/[0-9]+/gm) || []).pop() 

这个搜索在多行字符串的数量和需要的最后一个。如果没有找到数字，则返回空数组，该数组将返回undefined,pop()。听起来正是你所需要