e4x: simplest way to tell if an attribute exists

What's the simplest way to tell if an attribute exists?

p = <abc name="foo" />;


js>p.@name.length()
1
js>p.@zebra.length()
0

I can use @attr.length() but was wondering if there is an isAttributePresent() or som开发者_StackOverflow中文版ething.

NOTE: This is not in a browser, this is just a javascript interpreter based on core Mozilla Javascript 1.8 with E4X enabled.

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You can use

'@name' in p

This will return true or false depending on existence of said attribute.