An attempt has been made to invoke JSON.stringify with a value that is not valid. The value argument, an array or object, contains a circular reference.
To correct this error
The code in this example will cause a runtime error because john has a reference to mary and mary has a reference back to john.
var john = new Object();
var mary = new Object();
john.sister = mary;
mary.brother = john;
// This line will cause a runtime error.
var error = JSON.stringify(john);