Reference

Objects are never copied. They are passed around by reference.

// Imagine I had a pizza
var myPizza = { slices: 5 };
// And I shared it with You
var yourPizza = myPizza;
// I eat another slice
myPizza.slices = myPizza.slices - 1;
var numberOfSlicesLeft = yourPizza.slices;
// Now We have 4 slices because myPizza and yourPizza
// reference to the same pizza object.
var a = {},
  b = {},
  c = {};
// a, b, and c each refer to a
// different empty object
a = b = c = {};
// a, b, and c all refer to
// the same empty object