如何强制字符串中的最后一个字符在一定范围内？

Question

I have a regular expression which allows the value range '1111' - '999999', excluding any instances of '0':

^([1-9]){4,6}$

This is working for me, except my requirement has been modified. I now have to disallow the last '9' in the range, so that the maximum value of the last character is '8', eg

1111 - 9998, or 1111 - 99998, or 1111 - 999998

How can I modify this regular expression to meet the new criteria?

Answer 1

这个怎么样

^([1-9]){3,5}[1-8]$

Answer 2

First option:

^[1-9]{3,5}[1-8]$ 

Second option:

^(?!.*9$)[1-9]{4,6}$ 

Negative lookahead (?!.*9$) does not allow 9 to be at the end.

Third option:

^(?!.*0)(?!.*9$)\d{4,6}$ 

Negative lookahead (?!.*0) does not allow 0 to be in text at all.