The text is quite misleading. Where it says "When using Object literals, if we copy an object and change a property or a method that method/property will be changed for all instances."
And in the code, there is only one instance. No copying has taken place, but there are two references to the same object.
Agreed, anyone who uses this as the beginner tutorial it is will be confused for a long time by words like "copy" and "clone" used to mean variable assignment. This is terrible teaching, or somehow the author has an exotic mental model of what the computer is doing.
Agreed. I could see how that line could be confusing. Why don't we change it for the better in that case? How about something like this:
In the example above we create a new variable sally, and assign it the value bill. Both sally and bill reference the same spot in memory. As such we can't change bill out w/ out changing Sally, specifically when a change is made to an object literal it will affect that object across the entire script.
How about: In the example above we create a new variable sally, and make it equal to bill. Both sally and bill now reference the same object in memory. Changes made via one affect both of them.
And in the code, there is only one instance. No copying has taken place, but there are two references to the same object.