On Tuesday, January 8, 2013, Tab Atkins Jr. wrote: > On Tue, Jan 8, 2013 at 12:40 PM, Andrea Giammarchi > <[email protected] <javascript:;>> wrote: > > So, I am playing with FF 18 and I have this behavior: > > > > var a = new Proxy([], {}); > > console.log(a instanceof Array); // true > > console.log(Array.isArray(a)); // true > > console.log({}.toString.call(a));// [object Array] > > > > Function.apply(null, a); // anonymous() > > > > Cool uh? there's no way to tell that a is not actually an array but > rather a > > proxy: awesome!!! > > > > Now I go in that dark place called DOM: > > > > var n = new Proxy(document.createElement("p"), {}); > > console.log(n instanceof HTMLElement);// true > > console.log({}.toString.call(n)); // true > > document.body.appendChild(n); > > // Error: Could not convert JavaScript argument arg 0 > > [nsIDOMHTMLBodyElement.appendChild] > > > > Is this meant? 'cause it looks lik ewe have half power here and once > again > > inconsistencies ... thanks for explaining me this. > > As Francois points out, this is a known problem. DOM objects don't > live solely in JS - they tend to have C++ backing classes that do a > lot of the heavy lifting. Your average JS object, without such C++ > support, simply won't work with the JS methods that, when they call > back into C++, expect to see the DOM C++ classes. > > This is a problem elsewhere, too - Web Components really wants to make > it easy to subclass DOM objects, but we've had to twist ourselves into > knots to do it in a way that alerts the C++ side "early enough" that > it can create the new objects with appropriate backing C++ classes. > > It can potentially be solved by efforts like moving the DOM into JS, > which browsers are pursuing to various degrees, but it's a hard > problem on the impl side. Meanwhile, there is unforgeable magic > behind DOM objects, and nothing we can really do about it. >
Well, we can attempt (as much as is practicable at any point) to avoid "blessing" this split and the crazy behaviors it begets. Designing for DOM-in-JS world is the only way to stay sane. What JS-in-DOM can't do that DOM needs, we should add. But not much more.
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