Prevent limited lookbehinds in older vers of vim

Author: amadeus

syntax/javascript.vim

@@ -97,7 +97,11 @@ syntax match   jsRegexpOr         "\v\<@!\|" contained
 syntax match   jsRegexpMod        "\v\(@<=\?[:=!>]" contained
 syntax cluster jsRegexpSpecial    contains=jsSpecial,jsRegexpBoundary,jsRegexpBackRef,jsRegexpQuantifier,jsRegexpOr,jsRegexpMod
 syntax region  jsRegexpGroup      start="\\\@<!(" skip="\\.\|\[\(\\.\|[^]]\)*\]" end="\\\@<!)" contained contains=jsRegexpCharClass,@jsRegexpSpecial keepend
-syntax region  jsRegexpString     start=+\%(\%(\%(return\|case\)\s\+\)\@<=\|\%(\%([)\]"']\|\d\|\w\)\s*\)\@<!\)/\(\*\|/\)\@!+ skip=+\\.\|\[\%(\\.\|[^]]\)*\]+ end=+/[gimy]\{,4}+ contains=jsRegexpCharClass,jsRegexpGroup,@jsRegexpSpecial,@htmlPreproc oneline keepend
+if v:version > 703 || v:version == 603 && has("patch1088")
+  syntax region  jsRegexpString     start=+\%(\%(\%(return\|case\)\s\+\)\@50<=\|\%(\%([)\]"']\|\d\|\w\)\s*\)\@50<!\)/\(\*\|/\)\@!+ skip=+\\.\|\[\%(\\.\|[^]]\)*\]+ end=+/[gimy]\{,4}+ contains=jsRegexpCharClass,jsRegexpGroup,@jsRegexpSpecial,@htmlPreproc oneline keepend
+else
+  syntax region  jsRegexpString     start=+\%(\%(\%(return\|case\)\s\+\)\@<=\|\%(\%([)\]"']\|\d\|\w\)\s*\)\@<!\)/\(\*\|/\)\@!+ skip=+\\.\|\[\%(\\.\|[^]]\)*\]+ end=+/[gimy]\{,4}+ contains=jsRegexpCharClass,jsRegexpGroup,@jsRegexpSpecial,@htmlPreproc oneline keepend
+endif
 syntax match   jsNumber           /\<-\=\d\+\(L\|[eE][+-]\=\d\+\)\=\>\|\<0[xX]\x\+\>/
 syntax keyword jsNumber           Infinity
 syntax match   jsFloat            /\<-\=\%(\d\+\.\d\+\|\d\+\.\|\.\d\+\)\%([eE][+-]\=\d\+\)\=\>/