If you haven't seen the prior versions, XRegExp is an MIT-licensed JavaScript library that provides an augmented, cross-browser implementation of regular expressions, including support for additional modifiers and syntax. Several convenience methods and a new, powerful recursive-construct parser that uses regex delimiters are also included. Here's what you get beyond the standard JavaScript regex features: Added regex [...]

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The bottom line of this blog post is that Internet Explorer incorrectly increments a regex object's lastIndex property after a successful, zero-length match. However, for anyone who isn't sure what I'm talking about or is interested in how to work around the problem, I'll describe the issue with examples of iterating over each match in [...]

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Here's one of the oddest and most significant regex bugs in Internet Explorer. It can appear when using optional elision within lookahead (e.g., via ?, *, {0,n}, or (.|), but not +, interval quantifiers starting from one or higher, or alternation without a zero-length option). An example in JavaScript: /(?=a?b)ab/.test("ab"); // Should return true, but IE 5.5 [...]

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Regexes suck at math. To a regex engine, the characters 0 through 9 are no more special than any others. I should mention that there are a couple exceptions. Perl and PCRE allow dynamic code to be run at any point during the matching process, which presents a great deal of extra potential. Perl does this [...]

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Firefox includes a non-standard JavaScript extension that makes regular expressions callable as functions. This serves as a shorthand for calling a regex's exec method. For example, in Firefox /regex/("string") is equivalent to /regex/.exec("string"). Early ECMAScript 4 proposals indicated this functionality would be added to the ES4 specification, but subsequent discussion on the ES4-discuss mailing list [...]

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