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.