Why does outerHTML bring back comments?

Question

I have a jsfiddle here - http://jsfiddle.net/stevea/QpNbu/3/ - that collects the outerHTML for all elements that have class='active'. What amazes me is that even if I comment out some of the HTML, as in:

<!--      <div>'Some inner text'</div>  -->

outerHTML still brings it back! This can't still be in the DOM so I'm wondering where outerHTML is looking.

Thanks for any insight.

innerHTML will do the same thing – Smern Jul 13 '13 at 02:02 — Smern, Jul 13 '13 at 02:02

Zhanger · Accepted Answer · 2013-07-13T03:20:43.283

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Comments in HTML are ~~surprisingly~~, in fact, part of the DOM! If you look in this screen shot here:

web inspector

You'll see the google chrome web inspector renders it as part of the DOM (notice how the bottom bar shows it as a child of div#box1.active as well.)

For more concrete documentation, if you look at the possible Node.nodeTypes for DOM nodes on MDN, you'll see that the COMMENT_NODE is one of the valid types.

COMMENT_NODE 8

W3 also defines the Comment interface for the DOM:

This interface inherits from CharacterData and represents the content of a comment, i.e., all the characters between the starting ''. Note that this is the definition of a comment in XML, and, in practice, HTML, although some HTML tools may implement the full SGML comment structure.

edited Jul 13 '13 at 03:20

answered Jul 13 '13 at 02:16

Zhanger

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Surprisingly? It'd hardly be a complete model of the document if it omitted them. – Chris Morgan Jul 13 '13 at 03:06
@ChrisMorgan my bad, fixed – Zhanger Jul 13 '13 at 03:20
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It was surprising to me, and apparently to a lot of other people judging from all the upvotes the answer got. – Steve Jul 13 '13 at 07:17

Vaishak Suresh · Answer 2 · 2013-07-13T19:07:05.653

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HTML comments are part of the DOM, they just get ignored by the browser for display.

edited Jul 13 '13 at 19:07

answered Jul 13 '13 at 02:22

Vaishak Suresh

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That's somewhat contradictory – the browser constructs the DOM; if they're in the DOM, they obviously *weren't* ignored by the browser. – icktoofay Jul 13 '13 at 03:02
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I presume you mean "get ignored by the browser *for display*." – Chris Morgan Jul 13 '13 at 03:07

Why does outerHTML bring back comments?

2 Answers2