The above website can be used to detect regular expression syntax of JS online
In addition to a few well-known fixed characters representing positions:
^ : Match the beginning of the string and, in multiline searches, the beginning of a line.
$ : Match the end of the string and, in multiline searches, the end of a line.
\b:
Match a word boundary. That is, match the position between a \w character and a \W character or between a \w character and the beginning or end of a string. (Note, however, that [\b] matches backspace.)
\B: Match a position that is not a word boundary.
Another thing is to use regular expressions to determine the location to match, also called Zero-Width Test (zero-width assertion)
(?=p) :
A positive lookahead assertion. Require that the following characters match the pattern p, but do not include those characters in the match.
(?!p) ：
A negative lookahead assertion. Require that the following characters do not match the pattern p.
For (?=p)and(?!p) Use an example:
To be in url(skins/default/images/index/defaultMatch "default" in "/default/" in .png) and not "default" in "/"?
Regular expressions:(?!\/)default(?=\/)
in(?!\/)It means that it starts with "/",(?=\/)Indicates ending with "/"