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Re: html template string handler WAS: E4H and constructing DOMs

From: Ian Hickson <ian@hixie.ch>
Date: Mon, 11 Mar 2013 19:01:45 +0000 (UTC)
To: Ojan Vafai <ojan@chromium.org>
cc: "public-script-coord@w3.org" <public-script-coord@w3.org>
Message-ID: <Pine.LNX.4.64.1303111847460.15713@ps20323.dreamhostps.com>
On Mon, 11 Mar 2013, Ojan Vafai wrote:
> 
> I see two options:
> 1. Do E4H style parsing. (http://www.hixie.ch/specs/e4h/strawman)
> 2. Do <template> style parsing through the regular HTML parser.

The big disadvantage of #2 is that the HTML parser really isn't a good 
match for dynamic DOM creation. For example, there'd be no way to do the 
?= feature of E4X with an HTML parser (in E4X, @<input disabled?={foo}/> 
will create an <input> element with a disabled attribute if |foo| 
evaluates to true, and without one otherwise).

Also, I don't really see how to do safe injection with an HTML parser 
without an additional layer on top -- for example, what would you do with 
"<div {foo}>" or "<div></{foo}>" and so on?

It's also not clear how you would build up a DOM from other parts that 
have been previously parsed or created via JS. For example, today with DOM 
calls you can do:

   var input = document.createElement('input');
   input.value = foo;
   // ...
   var div = wrapInput(input);

   function wrapInput(input) {
     var div = document.createElement('div');
     div.appendChild(document.createTextNode('Name: '));
     div.appendChild(input);
     div.appendChild(document.createTextNode(' (required)'));
     return div;
   }

In E4H this would translate to:

   var input = @<input value={foo}/>;
   // ...
   var div = wrapInput(input);

   function wrapInput(input) {
     var div = @<div/>;
     div.appendChild(<>Name: </>);
     div.appendChild(input);
     div.appendChild(<> (required)</>);
     return div;
   }

(Or we could extend E4H to support substituting DOM nodes into element 
contents. I haven't done that in the strawman, but it seems reasonable to 
support, at a first glance.)

I don't see how you could really do this with a parser, short of invoking 
it a bunch of times for little snippets, which seems likely to be expensive.


(How would the above work in quasis? Would it invoke the HTML parser?)

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Monday, 11 March 2013 19:02:08 UTC

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