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.

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Answer 1

A cyclic data structure is a structure that holds a reference to itself (directly or indirectly). See also http://en.wikipedia.org/wiki/Circular_reference

Here is an example of such structure:

var c = { value: 'abc' };
c['c'] = c;
c['a'] = { value: c };

If you try to print its string representation recursively, you will end up with a stack overflow, because to print a value of c you must print the value of c.