We've seen that you cannot reassign a constant variable in the case of a number

or a string.

The same goes for any value of a constant variable.

You cannot reassign strings, numbers, booleans, objects, and arrays.

Unlike strings, numbers, and booleans, objects in arrays have methods and

properties that modify the objects or array.

Do they still work with const?

First we'll declare a variable, which is a constant called days.

This will contain an array with a single string "Monday".

Second we'll declare another constant variable

person that contains an object literal with a {first_name}.

Key, with the string "Imogen".

Let's attempt to modify these in the console here, first days.

Let's use the push method to add another day to the array.

It didn't error, it returned the number 2, meaning the new array length.

If we type days, and hit Enter, we get Monday and Tuesday returned.

Let's try and add a last_name property to the person object.

Again no error.

When we type person and hit Enter we get an object

literal back with the first_name and last_name properties.

So what's happening here?

Const doesn't prevent complex objects like arrays and objects from being modified.

It just prevents them from being reassigned or over written completely.

For example, when I attempt to override

person with another object literal.

It shows an error, because I'm attempting to re-assign person with a new object.

However, if I modified the first name.

To equal another value, Andrew, I don't get any errors.