CODEWITHSUNDEEP
javascriptregex
Prafull Dhadkar
Prafull Dhadkar

Reputation: 941

regex to allow space and restrict special characters at the beginning of a non empty string

I want to create a RegExp in javascript. The requirement is to allow spaces at the beginning of a string if the string is non-empty. also, I have to restrict some special characters at the beginning of the string.

Currently, I am using this RegExp -

 ^(?!^[=+-@]).*



these strings need to be passed from regexp test - 

foo
foo bar
       bar
       123bar
[email protected]



these string should fail - 
@foo
        @foo
'           ...spaces'
'' empty-string

Please help.

Upvotes: 1

Views: 1420

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626758

You can use

^(?! *[=+@-]| +$).*

Or, to match any kind of whitespaces:

^(?!\s*[=+@-]|\s+$).*

Details:

  • ^ - start of string
  • (?!\s*[=+@-]|\s+$) - a negative lookahead that fails the match if, immediately to the right from the current location, there is
    • \s*[=+@-] - zero or more whitespaces and then =, +, @, or -
    • | - or
    • \s+$ - one or more whitespaces till end of string
  • .* - zero or more chars other than line break chars as many as possible.

Upvotes: 2

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