帮助Regex - 点后需要最多3个数字(.)

Question

我需要一个匹配数字的正则表达式的帮助.点(.)后我需要最多3位数:

12345    ok
12       ok
12.1     ok
12.12    ok
12.123   ok
12.1234  Error
1.123456 Error

怎么做？提前致谢.

Answer 1

\d+(?:\.\d{1,3})?

说明:

\d+        # multiple digits
(?:        # start non-capturing group  
  \.       # a dot
  \d{1,3}  # 1-3 digits
)?         # end non-capturing group, made optional

Answer 2

^\d+(\.\d{1,3})?$