HTML with commented JavaScript code

Question

I am trying to parse a HTML code in order to extract all links in it. To avoid unavailable links I remove the commented code that begins with  .Here comes the problem: In the HTML code I may find some JavaScript code, for example:

<html>
<HEAD>
<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
if (document.images) {
  var pic2 = new Image(); // for the inactive image
  pic2.src = "pic2.jpg";
  var title2 = new Image();
  title2.src = "title2.jpg";
  }
...
-->

and the weird thing is that the js code is commented but it still works. So, if I remove that code, the result won't be as expected. What should I do in order to identify when I'm facing with unused commented code and when that commented code is functional?

Quentin · Accepted Answer · 2014-06-09 09:43:16Z

6

the weird thing is that the js code is commented but it still works

Those aren't comments. Is is just syntax allowed inside script (and style) elements that follows the comment syntax so that browsers which predate script and style don't render the code as text.

What should I do in order to identify when I'm facing with unused commented code and when that commented code is functional?

Write a real HTML parser, following the parsing specification, and then remove any comment nodes from the generated DOM.

As a dirty (but possibly quick) solution, you could just ignore comments inside elements marked as containing CDATA in the HTML 4.01 DTD.

edited Jun 9, 2014 at 9:43

answered Jun 9, 2014 at 9:27

Quentin

948k136 gold badges1.3k silver badges1.4k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Dani Grosu Over a year ago

Ok. Now things are clear to me. Thanx very much for your answer. I'll look for the best strategy.

Qantas 94 Heavy · Accepted Answer · 2014-06-09 09:51:23Z

0

the weird thing is that the js code is commented but it still works

There is nothing weird about it. The comments  only work in HTML, not JavaScript. Your above code will still work since you've put these comments within the <script> tags. The only difference it makes is that if the user has disabled JavaScript on his/her browser, he won't see the code printed on the browser (since HTML will parse those comments in the absence of JavaScript).

edited Jun 9, 2014 at 9:51

Qantas 94 Heavy

16k31 gold badges74 silver badges89 bronze badges

answered Jun 9, 2014 at 9:27

Shinu Jacob

1114 bronze badges

1 Comment

Quentin Over a year ago

This doesn't answer the question (which is about identifying which  are comments and which are not). You're also wrong, browsers which support JS but have it disabled (as well as any browser which doesn't support JS written since about 1998) won't render the text inside scripts. It is only browsers which predate the addition of script to HTML that will.

pankaj · Accepted Answer · 2014-06-09 09:34:22Z

-1

You need to comment out the whole <script> block. e.g.

 <!-- <script>
       ...some javascript code... 
</script> -->

answered Jun 9, 2014 at 9:34

pankaj

1,3663 gold badges17 silver badges27 bronze badges

2 Comments

Quentin Over a year ago

The question is asking how to identify  sequences which are comments and which are not. It isn't asking how to comment out a script.

pankaj Over a year ago

sorry, completely missed that part.

Collectives™ on Stack Overflow

HTML with commented JavaScript code

3 Answers 3

1 Comment

1 Comment

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related