字母数字和空格正则表达式，但字符串的开头和结尾没有空格

Question

I want to write a regex that may contains alphabets or number or spaces between word and must be of length between 3 to 50 but not spaces on start and end of string. This is my regex:

/^[^-\s]([a-z0-9]|[a-z0-9\s-]){3,50}[^-\s]+$/i

Valid strings:

uma
umair
umair K

Invalid strings:

 uma
u
um
umair 

The last example has a trailing space.

Answer 1

^(?=.{3,50}$)[^\W_]+(?: [^\W_]+)*$

• ^ Assert position at the start of the string
• (?=.{3,50}$) Positive lookahead ensuring between 3 and 50 characters exist before the end of the line
• [^\\W_]+ Match any word character except _ one or more times
• (?: [^\\W_]+)* Match a space followed by one or more word characters, any number of times
• $ Assert position at the end of the line

 var r = /^(?=.{3,50}$)[^\\W_]+(?: [^\\W_]+)*$/ var a = [ 'uma','umair','umair K', //valid ' uma','u','um','umair ' //invalid ] a.forEach(function(s){ console.log(r.test(s) ? `Valid: ${s}` : `Invalid: ${s}`) }) 

Alternatives:

^[^\W_][a-zA-Z\d ]{1,48}[^\W_]$

Answer 2

A literal translation of your requirements looks like this:

!/[^a-zA-Z\d\s]/.test(str) &&
str.length >= 3 && str.length <= 50 &&
!/^\s/.test(str) &&
!/\s$/.test(str))

Why cram everything in one regex?