javascript - Matching special characters with Regex lookahead -


i receiving messages have underscores:

  _omgitworks_

however, when these messages formatted our html wire formatter receive them backslashes infront of underscores:

  \_omgitworks\_

i created following regex capture backslashes , remove them text tokenizes correctly:

rawinput.replace(/\\([_])/g, '$1');

however, there edge case of when user italicizes text. when user utalicizes text, receive messages no backslashes underscores - , want remove underscores. received text looks like:

_omgitworks_

i trying design regex matches backslash followed underscore , replaces backslash (but not underscore) or if there underscore no bachslash, matches underscore.

i tried implement using lookaheads:

var regex = /\\(?=_)|_/g; var string = '\\_omgitworks\\_' string.replace(regex, '') >>> "omgitworks"

but removing backslash , underscore instead of underscore. there nuances lookaheads overlooking?

you can use following regex:

\\(_)|(^|[^\\])_

and replace $1$2.

see regex demo

explanation:

  • \\(_) - first alternative matching \ followed _ (capture group 1)
  • | - or...
  • (^|[^\\])_ - alternative matching start of string or character other \ (captured group 2) followed underscore.

in relacement part, restore captures using backreferences. in js, failed groups pre-populated empty string, safe use if capture groups happen empty.

var re = /\\(_)|(^|[^\\])_/g;   var str = '_omgitworks_\n\\_omgitworks\\_';  var result = str.replace(re, '$1$2');  document.body.innerhtml = "<pre>"+ result + "</pre>";


Comments

Post a Comment

Popular posts from this blog

java - pagination of xlsx file to XSSFworkbook using apache POI -

right in code, reading xlsx file, xssfworkbook, , writing database. but, when size of xlsx file increases, causes outofmemory error. can not increase server size, or divide xlsx file pieces. tried loading workbook using file (instead of inputstream), didn't either. i looking way read 10k rows @ time (instead of entire file @ once) , iteratively write workbook , database. is there way apache poi? poi contains called "eventmodel" designed purpose. it's mentioned in faq : the ss eventmodel package api reading excel files without loading whole spreadsheet memory. require more knowledge on part of user, reduces memory consumption more tenfold. based on awt event model in combination sax. if need read-only access, best way it. however, may want double check first if issue somewhere else. check out this item : i think poi using memory! can do? 1 comes quite lot, reason isn't might think. so, first thing check - what's source of prob...
Read more

Unlimited choices in BASH case statement -

consider simple bash snippet: case $option in 1) image=${options[0]%.tar} ;; 2) image=${options[1]%.tar} ;; 3) image=${options[2]%.tar} ;; 4) image=${options[3]%.tar} ;; *) echo "invalid option" exit 1 esac in real script numbers goes 30. makes pretty long. can somehow specify cases variable? something this: case $option in $i) image=${options[$(($i-1))]%.tar} any pointer appreciated. you can match against multiple patterns in single clause: case $option in 1|2|3: echo "$option one, 2 or three" ;; esac if still typing you, can use simple pattern matching: case $option in # following matches # - single-digit numbers 0-9 # - two-digit numbers starting either 1 or 2 # - number 30 [0-9]|[12][0-9]|30) image=${options[$(($option-1))]%.tar} ;; *) echo "invalid option" 1>&2 exit 1 esac
Read more

apache - How do I stop my index.php being run twice for every user -

we've got webapp initial html served using apache , php. i noticed index.php being run twice every request. seems caused / effected rewrite rules in our .htaccess - rewritecond %{http_host} ^(www\.|hotels\.)ourdomain\.com$ [nc,or] rewritecond %{server_name} ^(www\.|hotels\.)ourdomain\.com$ [nc] rewriterule (.*) http://ourdomain.com/$1 [r=301] rewriterule ^hotels/([^/]+)/?\??(.*)$ ?d=$1&$2 [qsa] the final rule moving parameter url path query string. i.e. http://ourdomain.com/hotels/vegas?someparam=1 becomes http://ourdomain.com?d=vegas&someparam=1 if go directly query string version index.php run once. if use url redirected, index.php run twice (i'm checking adding error_log('end of index.php') file). so example going http://ourdomain.com/hotels/paris hits file twice http://ourdomain.com?d=paris hits once. i've seen this question , had @ blog mentioned , , can't find empty string url's (i've tried using yslow process). ...
Read more