Can anyone Explain the output of this javascript code snippet

Question

Please explain the output of the following code - bit confused with Javascript pass-by-reference.

var foo = {
  n: 1
};
var bar = foo;

foo.x = foo = {
  n: 2
};

console.log(foo); //{n:2}
console.log(bar); // {n:1, x:{n:2}}