检查字符串是否在字符串中的任何位置包含1-3个.-_字符

Question

I am trying to create a regex that checks a string and will match a dot, dash or underscore. I only want it to allow a maximum of 3 otherwise it should not match the string.

For example if I enter qwerty-123-123-123 that is okay.

If I enter something-123_world that is okay.

However if I enter qwerty-123-_whatever-something this should not match.

Current regex

My current regex matches the specific characters I want but I can't seem to figure out how to only allow 3 maximum. I thought {1,3} was the answer but that didn't seem to work. I also had a look at ?= positive lookups but not sure if that's correct / even able to get it to do what I want.

Answer 1

You may use

/^[^-_.]*(?:[-_.][^-_.]*){1,3}$/

See the regex demo

Details

• ^ - start of string
• [^-_.]* - any 0+ chars other than - , _ and .
• (?:[-_.][^-_.]*){1,3} - one, two or three occurrences of
  • [-_.] - a - , _ or .
  • [^-_.]* - any 0+ chars other than - , _ and .
• $ - end of string.

Answer 2

The other option apart from Regex would be to use JavaScript!

 let str1 = 'qwerty-123-123-123'; let str2 = 'something-123_world'; let str3 = 'qwerty-123-_whatever-something'; const regex = /[._-]/g; let min = 1; let max = 3; function validate(txt) { var len = txt.match(regex).length; if(len >= min && len <= max) return true; return false; } console.log(validate(str1) ? 'Valid' : 'Invalid'); console.log(validate(str2) ? 'Valid' : 'Invalid'); console.log(validate(str3) ? 'Valid' : 'Invalid');