如何在JavaScript中使用多维数组？

I have a multi-dimensional array, no problem. How do I interrogator one of the arrays in order to ascertain if it actually holds any data? I am working with VS 2008 and what I can see in the debugger is, lets call the element x, is x{...}. However, if I try and use x.length i get the message 'undefined' - so how do I ascertain if the array has nothing in it?I have a multi-dimensional array, no problem. H