Why does changing one array alters the other?

Question

Consider this tiny bit of javascript code:

var a = [1, 2, 3],
    b = a;

b[1] = 3;

a; // a === [1, 3, 3] wtf!?

Why does \"a\" change when

Answer 1

Assigning an array does not create a new array, it's just a reference to the same array. Numbers and booleans are copied when assigned to a new variable.