e4x: how to best check existence of an attribute?

Question

I know I can do it with the length() method:

>x = <a attr1='33' />
>x.@attr1
33
>[email protected]()
1
>[email protected]()
0

so I could use

if ([email protected]() > 0)
{
    .... do something ....
}

but is there a more appropriate way?

Answer 1

Never mind, I found the answer by poring through the Ecma-357 standard, particularly the XML.prototype.* and XMLList.prototype.* sections 13.4 and 13.5.

It's the hasOwnProperty() method:

js>x = <a attr1='33' ><item>gumball!</item></a>
<a attr1="33">
  <item>gumball!</item>
</a>
js>x.@attr1
33
js>x.hasOwnProperty('@attr1');
true
js>x.hasOwnProperty('@attr2');
false
js>x.hasOwnProperty('item');
true
js>x.hasOwnProperty('mongoose');
false