Test for existence of nested JavaScript object key

If I have a reference to an object:

var test = {};

that will potentially (but not immediately) have nested objects, something like:

{level1: {level2: {level3: "level3"}}};

What is the best way to check for the existence of property in deeply nested objects?

alert(test.level1); yields undefined, but alert(test.level1.level2.level3); fails.

I’m currently doing something like this:

if(test.level1 && test.level1.level2 && test.level1.level2.level3) {
    alert(test.level1.level2.level3);
}

but I was wondering if there’s a better way.