Cleaning whitespace from HTML with RegEx

Question

Is it possible for a RegEx to clean up whitespace in HTML?

For example:

<p><b>foo</b> <i>bar</i></p>
<p>foo</p> <p>bar</p>

On the first line, the space between the closing b and opening i tag is valid (although it could be a  ), however on the second line it is whitespace that I wish to clean up as it shouldn't have any semantic value.

Perhaps this would be better solved with DOM traversal?

ziesemer · Accepted Answer · 2011-12-23 15:15:41Z

5

Seems like something like HTML Tidy would be a better bet for what you're looking for - rather than needing to re-create all the potentially complex rules (such as your first whitespace in the example being significant, but not the 2nd, etc.)

Otherwise, I agree - DOM traversal would be a much better approach than regular expressions - especially if your HTML is already XHTML compliant and can be easily traversed as XML.

answered Dec 23, 2011 at 15:15

ziesemer

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3 Comments

Dave Over a year ago

I had a quick hunt around for a javascript implementation of HTML Tidy, but no luck, so DOM traversal it is. I need this to run as fast as possible, so hopefully IE won't cause too many issues.

ziesemer Over a year ago

Why would you bother doing this in JavaScript? Who will it benefit? All of the HTML will already have been transmitted to the client and rendered by the browser, so you won't be saving anything in terms of bandwidth or browser rendering.

Dave Over a year ago

Little extra background then, I'm fiddling around with a contenteditable div and the diff-match-patch library. Depending on browser implementation of contenteditable, I get different amounts of whitespace, resulting in never ending diffs as I go back and forth to the different browsers. Easiest workaround I can think of is to strip the whitespace entirely.

Niko Riitala · Accepted Answer · 2011-12-23 19:43:12Z

0

First I have to quote ;) "asking regexes to parse arbitrary HTML is like asking Paris Hilton to write an operating system" Then back to the business. You could try different regexes to tags (although, I'd doubt this is valid method):

sed -e 's/<p>\ </<p></g'

That removes <p>(whitespace)<(whatever_tag) whitespace.

Otherwise, I too agree with the DOM traversal.

answered Dec 23, 2011 at 19:43

Niko Riitala

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