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, - , .

, , , . .

replacer JSON-, , meetup:

let room = {
  number: 23
};

let meetup = {
  title: "",
  occupiedBy: [{name: ""}, {name: ""}],
  place: room
};

//  
room.occupiedBy = meetup;
meetup.self = meetup;

alert( JSON.stringify(meetup, function replacer(key, value) {
  /*   */
}));

/*    :
{
  "title":"",
  "occupiedBy":[{"name":""},{"name":""}],
  "place":{"number":23}
}
*/

let room = {
  number: 23
};

let meetup = {
  title: "",
  occupiedBy: [{name: ""}, {name: ""}],
  place: room
};

room.occupiedBy = meetup;
meetup.self = meetup;

alert( JSON.stringify(meetup, function replacer(key, value) {
  return (key != "" && value == meetup) ? undefined : value;
}));

/*
{
  "title":"",
  "occupiedBy":[{"name":""},{"name":""}],
  "place":{"number":23}
}
*/

replacer (key, value), -: {"": meetup}.

value == meetup, undefined. replacer , meetup, key != "".