Javascript Regular Expressions match Chinese characters, numbers, letters, and underscores _ basics-js tutorial

Javascript Regular Expression detection only contains Chinese characters, numbers, letters, and underscores. It cannot start or end with or after an underscore, for more information, see javascript Regular Expressions. Only Chinese characters, numbers, letters, and underscores are allowed.

I encountered a user name check problem and checked it. The following is a summary example:

The Code is as follows:

Var reg =/^ (?! _)(?!. *? _ $) [A-zA-Z0-9 _ \ u4e00-\ u9fa5] + $ /;
If (! Reg. test (string of the actual value )){
Alert ('enter 5-24 characters: Chinese characters, English letters, numbers, and "_". Chinese characters are recommended ');
}