Javascript正则表达式 - 开头没有空格+中间允许空格

Question

I would like to have a regex which matches the string with NO whitespace(s) at the beginning. But the string containing whitespace(s) in the middle CAN match. So far i have tried below

[^-\s][a-zA-Z0-9-_\\s]+$

Debuggex Demo

Above is not allowing whitespace(s) at the beginning, but also not allowing in the middle/end of the string. Please help me.

Answer 1

In your 2nd character class, \\\\s will match \\ and s , and not \\s . Thus it doesn't matches a whitespace. You should use just \\s there. Also, move the hyphen towards the end, else it will create unintentional range in character class:

^[^-\s][a-zA-Z0-9_\s-]+$

Answer 2

You need to use this regex:

^[^-\s][\w\s-]+$

• Use start anchor ^
• No need to double escape \\s
• Also important is to use hyphen as the first OR last character in the character class.
• \\w is same as [a-zA-Z0-9_]

Answer 3

在开头使用 \\S

^\S+[a-zA-Z0-9-_\\s]+$

Answer 4

If you plan to match a string of any length (even an empty string) that matches your pattern and does not start with a whitespace, use (?!\\s) right after ^ :

/^(?!\s)[a-zA-Z0-9_\s-]*$/
  ^^^^^^

Or, bearing in mind that [A-Za-z0-9_] in JS regex is equal to \\w :

/^(?!\s)[\w\s-]*$/

The (?!\\s) is a negative lookahead that matches a location in string that is not immediately followed with a whitespace (matched with the \\s pattern).

If you want to add more "forbidden" chars at the string start (it looks like you also disallow - ) keep using the [\\s-] character class in the lookahead:

/^(?![\s-])[\w\s-]*$/

To match at least 1 character, replace * with + :

/^(?![\s-])[\w\s-]+$/

See the regex demo . JS demo:

 console.log(/^(?![\\s-])[\\w\\s-]+$/.test("abc def 123 ___ -loc- ")); console.log(/^(?![\\s-])[\\w\\s-]+$/.test(" abc def 123 ___ -loc- "));

Answer 5

This RegEx will allow neither white-space at the beginning nor at the end of. Your string/word and allows all the special characters.

^[^\s].+[^\s]$

This Regex also works Fine

^[^\s]+(\s+[^\s]+)*$

Answer 6

试试这应该工作

[a-zA-Z0-9_]+.*$

Answer 7

/^[^.\\s]/

• try this instead it will not allow a user to enter character at first place
• ^ matches position just before the first character of the string
• . matches a single character. Does not matter what character it is, except newline
• \\s is space

Answer 8

If your field for user name only accept letters and middle of space but not for begining and end

User name: /^[^\\s][a-zA-Z\\s]+[^\\s]$/

If your field for user ID only accept letters,numbers and underscore and no spaces allow

user ID: /^[\\w]+$/

If your field for password only accept letters,number and special character no spaces allow

Password: /^[\\w@#&]+$/

Note: \\w content a-zA-Z , number , underscore ( _ ) if you add more character, add you special character after \\w .

You can compare with user ID and password field in password field im only add some special character ( @#& ).

India public thoko like 😁

Answer 9

I suggest below regex for this,

^[^\\s].*[^\\s]$

You can try regex in here