validating an object inside an array

Classic Servoy
1

Hello, I have a JavaScript question:

I have an object at certain positions of an Array and need to test if a position contains that object. If I do

if (anArray*[j])*
*```*
*I get an error "the undefined value has no properties" if there really is an object. If there is no object (array position is undefined) it passes OK.* 
*Does anyone know how to test for the existence of an object?*
*Thanks*
2

just out of my head
what does this:

if(anArray && anArray _&& anArray*[j])*_
_*```*_