ExtJS XTemplate and empty JSON parsing

How do you determine that a 开发者_JAVA技巧JSON object is empty in a XTemplate? I've tried

<tpl if="myObject != {}">
<tpl if="myObject">
<tpl if="myObject != undefined">

etc, but can't seem to find the right way to detect an empty object. Thanks.

<tpl if="!Ext.isEmpty(myObject)">