On Mar 25, 12:02 am, Glen <[email protected]> wrote:
> I would like to use Prototype's class inheritance to derive a class
> from Element as below:
> The current structure of Element and Class does not support such.
> I was wondering if anyone had anything more elegant.
I have the same issue - I want to create my own classes that "inherit"
from standard DOM elements, so I can do something like:
var Button = Class.create(Element, {
initialize: function($super, content) {
$super('button');
this.update(content);
}
});
document.body.appendChild(new Button("submit"));
But as you noted, Element in prototype is not a prototype Class that
can be extended using Class.create. I decided not to muck about with
that and instead write something else. So I create
Class.createElement() that works like as you would expect, with the
very serious caveat that you can't override most native methods (not
sure why - I can override some, but not others).
The implementation looks like this (and is mostly copied from
Class.create):
Class.createElement = function(tagname, impl) {
var IS_DONTENUM_BUGGY = (function() {
for ( var p in { toString : 1 }) {
// check actual property name, so that it works with
augmented
// Object.prototype
if (p === 'toString')
return false;
}
return true;
})();
return function() {
var elm = new Element(tagname);
properties = Object.keys(impl);
// IE6 doesn't enumerate `toString` and `valueOf` (among other
built-
in
// `Object.prototype`) properties,
// Force copy if they're not Object.prototype ones.
// Do not copy other Object.prototype.* for performance reasons
if (IS_DONTENUM_BUGGY) {
if (impl.toString != Object.prototype.toString)
properties.push("toString");
if (impl.valueOf != Object.prototype.valueOf)
properties.push("valueOf");
}
for ( var i = 0, length = properties.length; i < length; i++) {
var property = properties[i], value = impl[property];
if (Object.isFunction(value) &&
value.argumentNames()[0] ==
"$super") {
var method = value;
value = (function(m) {
return function() {
return elm[m].apply(this,
arguments);
};
})(property).wrap(method);
value.valueOf = method.valueOf.bind(method);
value.toString = method.toString.bind(method);
}
impl[property] = value;
}
Object.extend(elm,impl);
elm.initialize.apply(elm,arguments);
return elm;
};
};
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