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In my Angularjs application I need to have regular expression for two patterns for form validation with the following condition.

Pattern 1 :

The input box should accept alphanumeric with no space and it should also allow the user to use the characters like ~!@#$-_ any where in the string, except these characters non of the other characters should be allowed like (%, &, ^ etc). It should not allow leading/trailing whitespace also.

Examples :

 ab@4_w    :  valid
 sd!tye123  : valid
 sd%tye123  :  Invalid
 sd*tye123  :  Invalid

$scope.pattern1 = [\w~!@#\$-]+

Pattern 2: Should allow only alphanumeric with no space and no other characters including (_). It should not allow leading/trailing whitespace also.

Examples : 

  a4hgg5  : Valid
  a4_6hy   : Invalid
  a@yb    : invalid

$scope.pattern2 = [\w]+

$scope.pattern1 and $scope.pattern2 needs to be modified to meet my above requirements.

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  • Can you please precise the requirements? Can there be leading/trailing whitespace? Should a dot be allowed and where? Are ~!@#$-_ allowed anywhere in the string? If possible, please provide a fiddle to test. Commented Nov 14, 2016 at 8:21
  • Please clarify the requirements. You say you need _ in the question, but, in the comment, you say you do not want to match _. A JS fiddle would be of great help. Commented Nov 14, 2016 at 8:56

2 Answers 2

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It should not allow leading/trailing whitespace.

In both cases, add the ng-trim="false" attribute to the input element.

The input box should accept alphanumeric with no space and it should also allow the user to use the characters like ~!@#$-_ any where in the string, except these characters non of the other characters should be allowed like (%, &, ^ etc).

The pattern you have is correct, but escaping characters that do not have to be escaped is not recommended, use:

^[\w~!@#$-]+$

Where \w matches [a-zA-Z0-9_].

NOTE: if you pass the pattern as a string, do not add ^ and $ anchors, but double the backslashes: "[\\w~!@#$-]+".

Should allow only alphanumeric with no space and no other characters including (_).

It is much easier: ^[a-zA-Z]+$. Same comment about anchors as above applies.

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2 Comments

Wiktor, How can I restrict the allowed characters to be maximum 32 characters in the above regular expressions?
Use a limiting quantifier: ^[\w~!@#$-]{1,32}$ - {1,32} means repeat 1 to 32 times. To allow an empty string, use {0,32}. No spaces in between.
1

Try

^[\w~!@#\$-]+$

Explanation

  1. ^ Begin of string
  2. [\w~!@#\$-]+ Any number of the Characters you want, (note the need to escape $ like \$)
  3. $End of string

See in Action on Regex101. If you want empty strings to be valid, specify * instead of + for the quantifier. Also, when using \w you do not need to set the i flag, since it already covers both upper and lowercase letters.

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7 Comments

Even though in your solution [\w~!@#\$-]+ there is no underscore, but still underscore is getting allowed, how come?
Thats because \w is equivalent to [A-Za-Z0-9_], funny I know, i also dont know who specified this as an "word-character", but thats how it is...
Now if I need to accept all alpha numeric with no space and no underscore (_), what I have to do?
@MadasuK: You are contradicting yourself: But it should allow only the ~!@#$-_ along with alphanumerics. You stated you need to match _.
@WiktorStribiżew true, but for the sake of answering, you take away the \w and add A-Za-Z0-9 instead
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