OldWebKitFakeRadio.js

var formCheckedRadios = {};

function OldWebKitFakeRadio() {
	this._name = "";
	this._defaultChecked = false;
	this._checked = false;
}

OldWebKitFakeRadio.prototype = {
	get name() {
		return this._name;
	},
	set name( value ) {
		var name = String( value );

		if ( name !== this.name ) {
			var checked = this._checked;
			this.checked = false;
			this._name = name;
			this.checked = checked;
		}

		return value;
	},

	get defaultChecked() {
		return this._defaultChecked;
	},
	set defaultChecked( value ) {
		this._defaultChecked = !!value;

		if ( this._checked === undefined ) {
			this.checked = this._defaultChecked;
		}

		return value;
	},

	get checked() {
		return !!this._checked;
	},
	set checked( value ) {
		// Ignore if it seams same...
		if ( !value !== !this._checked ) {
			this._checked = !!value;

			if ( this._name ) {
				var key = ":" + this._name;
				var curr = formCheckedRadios[ key ];

				if ( this._checked ) {
					if ( curr && curr != this ) {
						curr._checked = false;
					}

					formCheckedRadios[ key ] = this;

				} else if ( curr == this ) {
					formCheckedRadios[ key ] = undefined;
				}
			}
		}

		return value;
	},

	cloneNode: function() {
		var elem = new OldWebKitFakeRadio();

		// Copy HTML "attributes"
		elem._name = this._name;
		elem._defaultChecked = this._defaultChecked;

		if ( this._name && this._checked ) {
			// WebKit do not allows multiple checked radios in same group.
			// Makes it to apear not checked (momentarily)...
			elem._checked = undefined;

			// Also unchecks the original one!
			this.checked = false;

		} else {
			elem.checked = this.checked;
		}

		return elem;
	}
}

function FakeRadio( real, fake ) {
	real = real || "<input name='foo' type='radio' checked='checked' />";

	if ( typeof real === "string" ) {
		var div = document.createElement("div");
		div.innerHTML = real;
		real = div.firstChild;
	}

	if ( !fake ) {
		fake = new OldWebKitFakeRadio();
		fake.name = real.name;
		fake.defaultChecked = real.defaultChecked;
		fake.checked = real.checked;
	}

	if ( !FakeRadio.debugging ) {
		return fake;
	}

	var o = { fake: fake, real: real };

	function check( a, b, msg ) {
		if ( a !== b ) {
			throw msg + " -> real: " + b + ", fake: " + a;
		}
	}

	["name", "defaultChecked", "checked"].forEach(function( name ) {
		o.__defineGetter__(name, function() {
			var a = fake[ name ];
			var b = real[ name ];
			check( a, b, "radio." + name );
			return a;
		});

		o.__defineSetter__(name, function( value ) {
			var a = ( fake[ name ] = value );
			var b = ( real[ name ] = value );
			check( a, b, "( radio." + name + " = " + value + " )" );
			return a;
		});
	});

	o.cloneNode = function() {
		return FakeRadio( real.cloneNode(false), fake.cloneNode() );
	};

	return o;
}

FakeRadio.debugging = false; // Turn it 'on' only in old WebKit (like Safari 4).

// Example:
var a = FakeRadio("<input name='radiotest' type='radio' checked='checked' />");

a.checked //-> true

var b = a.cloneNode();

a.checked //-> false
b.checked //-> false

b.defaultChecked = b.defaultChecked // (true)
b.checked //-> true