Improve handler

[eGavr]

Besides, what about this situation:

<tag></tag>

and

<tag/>

?

It seems, the contentHandler parses them just in the same way! Yes, they are identical for a browser, but in the point of view of parsing they are not identical, are they?

[aredridel]

They are -- the HTML5 parser only concerns itself with parsing to construct a DOM.

[eGavr]

Are you going to fix this situation?

[aredridel]

Does it need to be fixed? What's the use-case?

[eGavr]

Yes!
For example, when I want to transform my DOM tree back to html!

In the cases I've shown above, SAXparser parses them in the same way!
It is a little bit unfair on the hand of your SAXparser.

[danyaPostfactum]

SAXParser notifies about element start and element end, not about start tag and end tag. That's all.

Yes, they are identical for a browser, but in the point of view of parsing they are not identical

If you really need low-level parsing info, you can use Tokenizer.

For example, when I want to transform my DOM tree back to html!

There is a limited set of VOID elements, so it is easy to serialize. http://www.whatwg.org/specs/web-apps/current-work/multipage/syntax.html#serialising-html-fragments

[danyaPostfactum]

Example of producing HTML from SAX events:
https://gist.github.com/danyaPostfactum/ee94c3bf88b99fb94c4b
Example:

var SAXParser = require('html5').SAXParser;
var HtmlSerializer = require('./HtmlSerializer').HtmlSerializer;

var outStream = require('fs').createWriteStream("out.html");

var parser = new SAXParser();
var serializer = new HtmlSerializer(outStream);

parser.contentHandler = parser.lexicalHandler = serializer;

parser.parse('...');

[eGavr]

But how can I understand whether the tag is self closing?

[danyaPostfactum]

Just check it's name matches one of area, base, basefont, bgsound, br, col, embed, frame, hr, img, input, keygen, link, menuitem, meta, param, source, track or wbr element.

[eGavr]

But if someone is so bad person and want to parse an invalid input?

<bra/>?, for example?

[eGavr]

Thank you for the list of self closing text!

[danyaPostfactum]

<bra/>, for example?

According to spec, it will be interpreted as <bra>. You can check this in your browser.

Thank you for the list of self closing text!

See http://www.whatwg.org/specs/web-apps/current-work/multipage/syntax.html#serialising-html-fragments

[eGavr]

But I can try to parse this situation :

<br></br>

It will be for browser - <br>,but what will I receive after serialization?

In two cases I will receive the same, but two inputs were not the same.

Maybe it is necessary to add a parameter into one of your contentHandler's method, it will be true if the tag is self closing?

[danyaPostfactum]

Parser will ignore </br> tag.

In two cases I will receive the same, but two inputs were not the same.

Yes, invalid markup will be repaired. I already said about it. Even valid input markup may not match serialized output. Could you explain how do you want to use parser? Probably you need another tool.

[eGavr]

For example, I want to check the validity of input or as in my case I want to compare to HTML!
For me it is necessary to check the HTMLs as they are!

[danyaPostfactum]

For example, I want to check the validity of input

This parser is used in http://ace.c9.io/build/kitchen-sink.html (select HTML mode) for syntax checking.

parser.errorHandler = {
    error: function(message, location, code) {
        // Parse error
    }
};

For me it is necessary to check the HTMLs as they are!

Not sure what do you mean. I guess you have to write your own parser.