请检查以下内容:

(?=^.{8,}

Please check this out:

(?=^.{8,}

)
这部分意味着还有8个字符，并且匹配从输入的开头开始.

((?=.*\d)
均值包含一个数字.

|(?=.*\W+))
或包含非字母或数字的内容

(?![.\n])
不是以点或UNIX换行符开头.

(?=.*[A-Z])
至少包含一个大写字母.

(?=.*[a-z])
包含至少一个小写字母

.*

)
This part means has 8 more more characters, and the match starts at the start of input.

((?=.*\d)
Means contains a digit.

|(?=.*\W+))
Or contains something that is neither a letter or a digit

(?![.\n])
not starting with a dot or UNIX newline.

(?=.*[A-Z])
Contains at least one capital letter.

(?=.*[a-z])
Contains at least one lowercase letter

.*

完全由非换行符组成，并且匹配的组将包含整个字符串.

还要检查一些线程:
表单验证！ [此处 [此处 [这里 [

Consists entirely of non-newline characters and the matched group will contain the entire string.

Also check some threads:
Form validating![^]
Here[^]
Here[^]
and Here[^]