Define "cyclic data structures"

Question

At the JSON site it says

JSON does not support cyclic data structures, so be careful to not give cyclical structures to the JSON stringifier.

What does it mean by this? Can someone give me an example of such a data structure in Javascript?

Answer 1

var cyclic = {}; cyclic.somekey = cyclic; cyclic.another = "Hello world!"; 

Now you can do this, for example:

alert(cyclic.somekey.somekey.somekey.another);