[whatwg] JavaScript function for closing tags

Michael A. Peters mpeters at domblogger.net
Fri Oct 13 23:36:00 PDT 2017

There does not seem to be a JavaScript API for closing open tags.

This is problematic when dealing with WebVTT which does not require tags 
be closed.

Where it is the biggest problem is when the document is being served as 

I tried the following hack which seemed to be working:

cleandoc = document.implementation.createHTMLDocument("FuBar");
cleanbody = document.createElementNS("http://www.w3.org/1999/xhtml", 

Then I could do the following when with a WebVTT cue:

cleanbody.innerHTML = string;
return (cleanbody.innerHTML);

That *mostly* works but seems to sometimes fail when string contains 
entities, such as  

What happens is it returns an empty string.

Given that WebVTT is part of HTML5 and browser native html5 audio 
players don't support caption tracks forcing us to write our own 
implementations if we want captions with audio, it sure would be nice if 
there was a pure JavaScript way to just add closing tags to a string 
because there is never a guarantee valid WebVTT cue has closed tags 
which are required for XHTML sent as XML.

Seems to me that a JS native function to add missing closing tags would 
have more application than just WebVTT cues.

I looked for a jQuery filter that does it, but could not find one.

It also could be of benefit in emulating document.write() as many of 
Google's tools *still* require document.write() despite the issues with 
document.write() and XML having been known for 15+ years now.

Any chance of getting a parser into JavaScript that at least would be 
capable of closing open tags in a string passed to it?

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