====== Mutating Data ======
JavaScript has somewhat annoying rules on this. Deep copies are required if you wish to avoid mutating. 
----

<code javascript>
const one = [0, 1, 2];
const two = one;
two.push(3);

console.log(one);
console.log(two);
</code>
output:
<code javascript>
[ 0, 1, 2, 3 ]
[ 0, 1, 2, 3 ]
</code>
Note: slice works on arrays of primitives not objects

<code javascript>
const one = [0, 1, 2];
const two = one.slice();
two.push(3);

console.log(one);
console.log(two);
</code>

output:
<code javascript>
[ 0, 1, 2 ]
[ 0, 1, 2, 3 ]
</code>

But objects will still refer to the original arrays even with slice
<code javascript>
const one = [
    {
        name: 'kalen',
        age: 23
    },
    {
        name: 'kailyn',
        age: '22',
    }
];

const two = one.slice();
two[0].name = 'Patrick';

console.log(one);
console.log(two);
</code>
output:
<code javascript>
[ { name: 'Patrick', age: 23 }, { name: 'kailyn', age: '22' } ]
[ { name: 'Patrick', age: 23 }, { name: 'kailyn', age: '22' } ]
</code>
----