javascript regex-look behind alternative? I'll give you some usage examples: Start string: ["Test1","Test2","Test3"] Sixteen years later, ES6/ES2015 introduced Unicode mode (the u flag), sticky mode (the y flag), and the RegExp.prototype.flags getter.. In It tells the regex engine to temporarily step backwards in the string, to check if the text inside the lookbehind can be matched there. look at this expression / a(?=b) / . Just as lookahead is supported, negative and positive lookbehind should too. Would be a relief when implementing QSyntaxHighlighter ::highlightBlock(), at the present I need to make some awkward workarounds. Within this group the expression starts with a question mark Last modified: Jan 19, 2021, by MDN contributors. The difference is that lookaround actually matches characters, but then gives up the match, returning only the result: match or no match. This is of course not the case for Internet Explorer (which puts the version number right after the MSIE token), and for Opera after version 10, which has added a Version/VersionNumber token. Where match is the item Thanks, Nils. and finds that it is a positive lookahead and in this look ahead there It is a fixed string between two semi-colons, in the comment part of the User Agent. So I'm looking for any alternatives for positive lookbehind or even another regex which can do what I want. Most rendering engines put the version number in the RenderingEngine/VersionNumber token, with the notable exception of Gecko. Lookahead assertions are very important in constructing a practical One such case is using user agent sniffing as a fallback when detecting if the device has a touch screen. no match hence that is why they are called assertions. # (*positive_lookbehind:pattern) A zero-width positive lookbehind assertion. all users, all tracked, tracked desktop Lookbehind is similar, but it looks behind. Negative lookbehind: (?