I recently discovered that several compatibility implementations of
Object.keys() on the web will throw an error for DOM objects in
Internet Explorer 8 and lower. This differs from the current browsers
having a native implementation and how the ECMAScript 5th edition
defines the behaviour of Object.keys.
The problem lies with the hasOwnProperty() check, which is not a valid
method on Internet Explorer DOM objects because they aren't instances
of Object. The fix is very simple; "borrow" hasOwnProperty() from
Object.prototype.hasOwnProperty() instead. The fixed PrototypeJS
implementation would be:
function keys(object) {
if (Type(object) !== OBJECT_TYPE) { throw new TypeError(); }
var results = [];
for (var property in object) {
if (object.prototype.hasOwnProperty.call(object, property)) {
results.push(property);
}
}
return results;
}
I've outlined the issue in more detail on my blog:
http://whattheheadsaid.com/2010/10/a-safer-object-keys-compatibility-implementation.
Cheers,
Andy E
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