Part of the idea is to get away from named objects as much as possible, and grouping in a single array or object is much easier to search, amend, append or prepend, or delete entries from. Variables on the other hand can only be nulled, never deleted, as such.
One way to cater to both, global and reference object is with a constructor.
this.firstName = firstName;
this.lastName = lastName;
this.email = email;
this.phoneNumber = phoneNumber;
Now if we wish to instantiate a global variable reference,
john = new Person(" ... ", " ... ", " ... ", " ... ");
but if we just want to keep adding to the array,
contacts.push(new Person(" ... ", " ... ", " ... ", " ... "));