如何获得仅允许0000或空格的正则表达式

Question

我怎样才能获得只允许0000或空格的正则表达式,但不能同时使用两者

例子:

1. 0000000000000000000 - >好的;
2. 只有空格 - >好的;
3. 000000000 0000 - >不行;
4. afads0000 00 0fd - >不行;

Answer 1

^(?:0+| +)$

说明:

^      # Start of string
(?:    # Either match (but don't capture)...
 0+    # one or more zeroes
|      # or
 [ ]+  # one or more spaces
)      # End of non-capturing group (used to contain the alternation)
$      # End of string