Flagrant Badassery

A JavaScript and regular expression centric blog

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What the JavaScript RegExp API Got Wrong, & How to Fix It

Over the last few years, I've occasionally commented on JavaScript's RegExp API, syntax, and behavior on the ES-Discuss mailing list. Recently, JavaScript inventor Brendan Eich suggested that, in order to get more discussion going, I write up a list of regex changes to consider for future ECMAScript standards (or as he humorously put it, have […]

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An IE lastIndex Bug with Zero-Length Regex Matches

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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A JScript/VBScript Regex Lookahead Bug

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 […]

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JavaScript, Regex, and Unicode

Not all shorthand character classes and other JavaScript regex syntax is Unicode-aware. In some cases it can be important to know exactly what certain tokens match, and that's what this post will explore. According to ECMA-262 3rd Edition, \s, \S, ., ^, and $ use Unicode-based interpretations of whitespace and newline, while \d, \D, \w, […]

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When innerHTML isn’t Fast Enough

This post isn't about the pros and cons of innerHTML vs. W3C DOM methods. That has been hashed and rehashed elsewhere. Instead, I'll show how you can combine the use of innerHTML and DOM methods to make your code potentially hundreds of times faster than innerHTML on its own, when working with large numbers of […]

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