Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
In JavaScript, can (?=regex) and (?!regex) be used in the middle of a regular expression, or they must be used at the end of a regular expression? If they can be used in the middle, what’s the meaning of it?
(?=…)and(?!…)(lookaheads) asserts that the string after it matches/does not match the sub-regex, without actually consuming them. They can appear anywhere. For examplematches
but not
See http://www.regular-expressions.info/lookaround.html for detail.