What happens if you nest toJSON functions?

nesting_tojson.js

var obj = {
  foo: 'foo',
  toJSON: function() {
    return {
      bar: 'bar',
      toJSON: function() {
        return {
          baz: 'baz'
        };
      }
    };
  }
};

JSON.stringify(obj);

Spoiler: {"bar":"bar"}