You don't need a special API for this, this can be done with just normal javascript.
 
Example: 
 
var doc = currentDocument; 
var item = doc.getValue("Body"); 
print("Body: " + typeof item); 
 
 
console: 
 
HTTP JVM:    Body : com.ibm.xsp.model.domino.wrapped.DominoRichTextItem 
 
typeof is a standard method of javascript as given the loosely bound nature of its variables it is required from time to time, epically in validation.
 
Hope this helps.