javascript - 如何选择字符串中的最后一个数字？

Question

我有一个像这样的字符串:

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";

我想要2。

另一个例子:

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";

我想要2。

另一个例子:

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";

我想要 null，因为两个连续的 \n 破坏了该序列。

<小时/>

如您所见，我想要列表样式的最后一个数字。像这样:

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

我怎样才能做到这一点？

Answer 1

尝试这个模式

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

Demo

数字后面必须有一个点

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

说明:

^[\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