ToJSON

Let room = {
  number: 23
};

let meetup = {
  title: "Conference",
  date: new Date(Date.UTC(2017, 0, 1)),
  room
};

alert( JSON.stringify(meetup) );
/*
  {
    "title":"Conference",
*!*
    "date":"2017-01-01T00:00:00.000Z",  // (1)
*/!*
    "room": {"number":23}               // (2)
  }
*/

An object may provide method toJSON for to-JSON conversion. JSON.stringify automatically calls it if available.

Related concepts

ToJSON — Structure map

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ToJSON — Related pages: