在ActionScript中，什么是要检查一个XML节点属性是否存在的最佳方法是什么？
如果我有一些XML像这样：
If I have some xml like so:
<books>
<book title="this is great" hasCover="true" />
<book title="this is not so great" />
</books>
什么是在动作的最佳（或接受）的方法来检查hasCover属性写一些code对之前存在？
What's the best (or accepted) way in actionscript to check if the hasCover attribute exists before writing some code against it?
我想补充一些precisions。
Just to add some precisions.
如果您要检查该属性存在，即使它是空的，你一定要使用的hasOwnProperty：
If you want to check if the property exists even though it's empty you should definitely use hasOwnProperty :
var propertyExists:Boolean = node.hasOwnProperty('@hasCover');
检查内容的长度是以某种方式脏，将返回false，如果该属性的值为空。你甚至可以有一个运行时错误抛出，你会试图访问一个属性（长度）的情况下一个空对象（hasCover）的属性不存在。
Checking the length of the content is somehow dirty and will return false if the value of the attribute is empty. You may even have a run-time error thrown as you will try to access a property(length) on a null object (hasCover) in case the attribute doesn't exist.
如果你想测试，如果该属性存在并且该值设置你应该尝试两种首先是的hasOwnProperty ，以便值测试（最终运行时错误）的情况下，该属性被忽略不存在：
If you want to test if the property exists and the value is set you should try both starting with the hasOwnProperty so that the value test (eventual run-time error) gets ignored in case the attribute doesn't exist :
var propertyExistsAndContainsValue:Boolean = (node.hasOwnProperty('@hasCover') && node.@hasCover.length());