Why does this work? Object references in Javascript

Question

I\'ve finally been curious enough to find out why javascript does its voodoo magic to learn why not all object references are created equal.

Given the example:

Answer 1

The value of a that is assigned to b is a Number. The value assigned from c to d is a reference to an Object.

var a, b, c, d;
a = 100; // a has value 100, a number
b = a; // b has value 100, a number

c = {}; // c has value p, a reference to some object P
d = c; // d has value p, a reference to P

b = 10; // b has value 10, a number
d.e = 'f'; // P.e has value 'f', a string

Answer 2

All variables in JavaScript are not objects. There are native types as well.

c and d are not linked to one another. They are pointing to the same object reference. If you were to reassign d to something else, it will not affect c.

var c = {};
var d = c;
d = { foo: "bar" };

c === d // false

However, if you were to modify the object being referenced by c or d, it will modify the same object since c and d are both referring to the same object as in your example.

Answer 3

It looks to me that the difference is with b, you're reassigning the variable to a new object/value, while with d, you're modifying the existing object.