Javascript: regular expression to validate alphanumeric and special characters

Question

Javascript: regular expression to validate alphanumeric and special characters

Looking to create a regular expression for a string (company/organization name) with the following conditions:

No leading or trailing spaces
No double spaces in between
Shouldn't allow only a single character (alphanumeric or whitelisted)
Can start with an alphanumeric or whitelisted character
Shouldn't allow any whitelisted character to be entered multiple times

Here is the regex for these conditions:

/(?! )([a-zA-Z0-9_\.\-#&])+([a-zA-Z0-9_\.\-#&\s])*(?<! )$/

console.log(/(?! )([a-zA-Z0-9_\.\-#&])+([a-zA-Z0-9_\.\-#&\s])*(?<! )$/.test('_')); // shouldn't allow

console.log(/(?! )([a-zA-Z0-9_\.\-#&])+([a-zA-Z0-9_\.\-#&\s])*(?<! )$/.test('a')); // shouldn't allow

console.log(/(?! )([a-zA-Z0-9_\.\-#&])+([a-zA-Z0-9_\.\-#&\s])*(?<! )$/.test('abc   abc')); // shouldn't allow

console.log(/(?! )([a-zA-Z0-9_\.\-#&])+([a-zA-Z0-9_\.\-#&\s])*(?<! )$/.test('_123')); // works fine

console.log(/(?! )([a-zA-Z0-9_\.\-#&])+([a-zA-Z0-9_\.\-#&\s])*(?<! )$/.test('# abc')); // works fine

console.log(/(?! )([a-zA-Z0-9_\.\-#&])+([a-zA-Z0-9_\.\-#&\s])*(?<! )$/.test('abc abc!')); // works fine

console.log(/(?! )([a-zA-Z0-9_\.\-#&])+([a-zA-Z0-9_\.\-#&\s])*(?<! )$/.test('abc abc# abc')); // works fine

The current regex does not meet all the criteria and it is unclear what the issue with the regex is.

javascript regex

Answer 1

Answer №1

Feel free to utilize

/^(?=.{2})(?!(?:[^_.#&!-]*[_.#&!-]){2})[a-zA-Z0-9_.#&!-]+(?:\s[a-zA-Z0-9_.#&!-]+)*$/

Particulars

^ - beginning of the line
(?=.{2}) - the line must start with any two characters
```
(?!(?:[^_.#&!-]*[_.#&!-]){2})
```
- there should not be two instances of _.#&!- characters in the line
[a-zA-Z0-9_.#&-]+ - one or more allowed characters (excluding whitespace)
(?:\s[a-zA-Z0-9_.#&!-]+)* - zero or more occurrences of
- \s - one whitespace character
- [a-zA-Z0-9_.#&!-]+ - one or more letters, digits, and certain symbols
$ - end of the line.

Check out the JavaScript demonstration below

var rx = /^(?=.{2})(?!(?:[^_.#&!-]*[_.#&!-]){2})[a-zA-Z0-9_.#&!-]+(?:\s[a-zA-Z0-9_.#&!-]+)*$/;
console.log(rx.test('_')); // should not be allowed
console.log(rx.test('a')); // should not be allowed
console.log(rx.test('abc   abc')); // should not be allowed
console.log(rx.test('_123')); // should work fine
console.log(rx.test('# abc')); // should work fine
console.log(rx.test('abc abc!')); // should work fine
console.log(rx.test('abc abc# abc')); // should work fine

Answer 2

Feel free to utilize

/^(?=.{2})(?!(?:[^_.#&!-]*[_.#&!-]){2})[a-zA-Z0-9_.#&!-]+(?:\s[a-zA-Z0-9_.#&!-]+)*$/

Particulars

^ - beginning of the line
(?=.{2}) - the line must start with any two characters
```
(?!(?:[^_.#&!-]*[_.#&!-]){2})
```
- there should not be two instances of _.#&!- characters in the line
[a-zA-Z0-9_.#&-]+ - one or more allowed characters (excluding whitespace)
(?:\s[a-zA-Z0-9_.#&!-]+)* - zero or more occurrences of
- \s - one whitespace character
- [a-zA-Z0-9_.#&!-]+ - one or more letters, digits, and certain symbols
$ - end of the line.

Check out the JavaScript demonstration below

var rx = /^(?=.{2})(?!(?:[^_.#&!-]*[_.#&!-]){2})[a-zA-Z0-9_.#&!-]+(?:\s[a-zA-Z0-9_.#&!-]+)*$/;
console.log(rx.test('_')); // should not be allowed
console.log(rx.test('a')); // should not be allowed
console.log(rx.test('abc   abc')); // should not be allowed
console.log(rx.test('_123')); // should work fine
console.log(rx.test('# abc')); // should work fine
console.log(rx.test('abc abc!')); // should work fine
console.log(rx.test('abc abc# abc')); // should work fine

Javascript: regular expression to validate alphanumeric and special characters

Answer №1

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