Write a class Account that keeps its balance private, and follow the commands in the input.
What to build
A class whose balance can change only through its own methods.
Requirements
- The account starts at 0, and the balance is in a private field.
deposit N: add N and printdeposited N.withdraw N: if N is more than the balance, printinsufficient fundsand change nothing. Otherwise take it out and printwithdrew N.balance: printbalance N.
Input
Several lines, each a command.
Output
One line per command.
Constraints
There are from 1 to 100 commands. Every N is a whole number from 1 to 1000000.
Example
Input:
deposit 100
withdraw 30
balance
Output:
deposited 100
withdrew 30
balance 70
Why it works
Because #balance cannot be touched from outside, the rule against overdrawing lives in one place and cannot be bypassed. A getter makes reading the balance look like reading a property.
Examples
Example 1 · Input
deposit 100 withdraw 30 balance
Expected output
deposited 100 withdrew 30 balance 70
Example 2 · Input
withdraw 5 balance
Expected output
insufficient funds balance 0
Hints
Hint 1
class Account with a private field #balance = 0, and methods deposit(amount), withdraw(amount) and a getter balance.
Hint 2
withdraw should refuse (return false) when amount is more than the balance.
Hint 3
Read lines until prompt() gives null; Number(parts[1]) is the amount.
Solution
Show one correct solution (try it yourself first)
class Account {
#balance = 0;
deposit(amount) {
this.#balance += amount;
}
withdraw(amount) {
if (amount > this.#balance) return false;
this.#balance -= amount;
return true;
}
get balance() {
return this.#balance;
}
}
const account = new Account();
let line = prompt();
while (line !== null) {
const [command, text] = line.split(" ");
const amount = Number(text);
if (command === "deposit") {
account.deposit(amount);
console.log(`deposited ${amount}`);
} else if (command === "withdraw") {
console.log(account.withdraw(amount) ? `withdrew ${amount}` : "insufficient funds");
} else {
console.log(`balance ${account.balance}`);
}
line = prompt();
}