Regex - how to exclude single word?

Question

I am using http://www.position-absolute.com/articles/jquery-form-validator-because-form-validation-is-a-mess/ for validation. Validation rules are defined in a following way:

            "onlyLetterSp": {
                "regex": /^[a-zA-Z\ \']+$/,
                "alertText": "* Only letters"
            }

I would like to add new rule, which will exclude one single word. I have read some similar questions on StackOverflow and tried to declare it with something like this

"regex": /(?!exclude_word)\^[a-zA-Z\ \']+$/,

But it didn't work. Can you give me some advices how to do it?

Answer 1

This is a good time to use word boundary assertions, like @FailedDev indicated, but care needs to be exercised to avoid rejecting certain not-TOO-special cases, such as wordy, wordsmith or even not so obviously cases like sword or foreword

I believe this will work pretty well:

\b(?!\bword\b)\w+\b

This is the expression broken down:

\b        # assert at a word boundary
(?!       # look ahead and assert that what follows IS NOT... 
  \b      #   a word boundary
  word    #   followed by the exact characters `word`
  \b      #   followed by a word boundary
)         # end look-ahead assertion
\w+       # match one or more word characters: `[a-zA-Z0-9_]`
\b        # then a word boundary

The expression in the original question, however, matches more than word characters. [a-zA-Z\ \']+ matches spaces (to support multiple words in the input) and single quotes as well (for apostrophes?). If you need to allow words with apostrophes in them then use the following expression:

\b(?!\bword\b)[a-zA-Z']+\b

Answer 2

\b(?:(?!word)\w)+\b

Will not match the "word".

Answer 3

It's unclear from your question what you want, but I've interpreted it as "not matching input that contains a particular word". The regex for this is:

^(?!.*\bexclude_word\b)