Regex - Delete chars between

Question

Earlier I tried some regex to trim strings between  (included these tags as well), but no success.

Could you give me some informations about the problem?

@Johnsyweb That's just plain wrong. Comments in HTML cannot contain another comment, so you don't go into problems with ambiguous markup - comment is just text ended with "-->" sequence (sequence in any place in comment will end it, you can't escape it) — MBO, Feb 08 '13 at 09:31
@MBO: while in a comment, "-->" is unambiguously the end of a comment. However, "" onmouseover="alert('uh oh')">Ooh! Move over me!`. Even using regular expressions to parse *comments* is likely to be a bad idea. — Chris Morgan, Feb 08 '13 at 10:07
@ChrisMorgan Good point, I haven't considered start of comment inside tags... So it's still hard problem. — MBO, Feb 08 '13 at 10:09

score 2 · Answer 1 · edited Feb 08 '13 at 10:09

2

Regex to match HTML comments:

/<!--.*?-->/s

Explained demo here: http://regex101.com/r/qZ4uP9

edited Feb 08 '13 at 10:09

Bart Kiers

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answered Feb 08 '13 at 09:32

CSᵠ

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I took the liberty to add the `s` modifier: by default `.` does not match line break chars in most regex implementations (with `s` it does). – Bart Kiers Feb 08 '13 at 10:10
@BartKiers: thanx, appreciated – CSᵠ Feb 08 '13 at 11:49

score 2 · Answer 2 · answered Feb 08 '13 at 09:34

To match a comment in text that looks like the rule for XML comments (and very close to the HTML comments rule) you want something like this:

<!--.*?-->

Assuming that your language's RE engine supports non-greedy quantifiers. Removal requires repeatedly matching that across the whole input text and substituting for the empty string; the syntax for that depends on the language in question.

Without non-greedy quantifiers, things get more complex (NB, this is slightly off for HTML comments but you really don't want to learn the details of the difference):

<!--([^-]|-[^-])*-->

Be aware that -- is not something you should encounter in an XML comment unless it is followed by a >; this is part of the nature of XML comments…

Regex - Delete chars between

2 Answers2