Example of "sameness" in the context of mutability

areAccountsEqual.mutable.ts

/**
 * With two _objects_, check equality by checking whether they are in fact the same object i.e. the reference.
 */
const areAccountsEqual = (a: BankAccount, b: BankAccount) => a === b;

const elainesAccount = new BankAccount(100);
const georgesAccount = new BankAccount(100);

elainesAccount.checkBalance(); // 100
georgesAccount.checkBalance(); // 100

areAccountsEqual(elainesAccount, elainesAccount); // true
areAccountsEqual(elainesAccount, georgesAccount); // false (eventhough identical funds)

georgesAccount.withdraw(75);

elainesAccount.checkBalance(); // 100
georgesAccount.checkBalance(); // 25

areAccountsEqual(elainesAccount, elainesAccount); // true
areAccountsEqual(elainesAccount, georgesAccount); // false