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Regular Expressions Cookbook, 2nd Edition
book

Regular Expressions Cookbook, 2nd Edition

by Jan Goyvaerts, Steven Levithan
August 2012
Intermediate to advanced content levelIntermediate to advanced
609 pages
19h 16m
English
O'Reilly Media, Inc.
Content preview from Regular Expressions Cookbook, 2nd Edition

9.9. Remove XML-Style Comments

Problem

You want to remove comments from an (X)HTML or XML document. For example, you want to remove development comments from a web page before it is served to web browsers, or you want to perform subsequent searches without finding any matches within comments.

Solution

Finding comments is not a difficult task, thanks to the availability of lazy quantifiers. Here is the regular expression for the job:

<!--.*?-->
Regex options: Dot matches line breaks
Regex flavors: .NET, Java, XRegExp, PCRE, Perl, Python, Ruby

That’s pretty straightforward. As usual, though, JavaScript’s lack of a “dot matches line breaks” option (unless you use the XRegExp library) means that you’ll need to replace the dot with an all-inclusive character class in order for the regular expression to match comments that span more than one line. Following is a version that works with standard JavaScript:

<!--[\s\S]*?-->
Regex options: None
Regex flavor: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby

To remove the comments, replace all matches with the empty string (i.e., nothing). Recipe 3.14 lists code to replace all matches of a regex.

Discussion

How it works

At the beginning and end of this regular expression are the literal character sequences <!-- and -->. Since none of those characters are special in regex syntax (except within character classes, where hyphens create ranges), they don’t need to be escaped. That just leaves the .*? or [\s\S]*? in the middle of the regex to examine ...

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Publisher Resources

ISBN: 9781449327453Supplemental ContentErrata Page