An object can be a property of another object, thus creating an object hierarchy. Suppose an object a has two object properties, b and c. The object b has two properties, d and e, while the object c has four properties, f, g, h, and i. Let's assume that d is 16, e is 42, f is true, g is "king", h is 13, and i is 10. The following expressions are references to various properies in this object hierarchy:

alert(a.b.d) // prints 16
alert(a.b.e) // prints 42
alert(a.c.f) // prints true
alert(a.c.g) // prints king
alert(a.c.h) // prints 13
alert(a.c.i) // prints 10

A property belongs to an object, and only to one object. A variable may be named exactly like a property of an object. The following statement is valid:

d = a.b.d;

However, a variable cannot have the same name as an object at the same level (scope). The following statement is not valid:

a = a.b.d;

It's good practice to avoid repeating names.

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