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:

var a, b, c, d;
a = 100; b = a;

c = {}; d = c;

b = 10; d.e = 'f';

console.log(a, b); // outputs 100, 10
console.log(c, d); // outputs object => e = 'f', object => e = 'f'

If all variables in javascript are objects, then what makes the use case with c and d cast explicitly as an Object so different than defining a and b as Number? Or, why will c and d be linked to one another, and not a and b?

Answer 1

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.