Add TypeScript examples

Author: tshemsedinov

TypeScript/1-traditional.ts

@@ -0,0 +1,97 @@
+abstract class AccountCommand {
+  public account: BankAccount;
+  public amount: number;
+  public operation: string;
+
+  constructor(account: BankAccount, amount: number, operation: string) {
+    this.account = account;
+    this.amount = amount;
+    this.operation = operation;
+  }
+
+  abstract execute(): void;
+  abstract undo(): void;
+}
+
+class Withdraw extends AccountCommand {
+  constructor(account: BankAccount, amount: number) {
+    super(account, amount, 'withdraw');
+  }
+
+  execute(): void {
+    this.account.balance -= this.amount;
+  }
+
+  undo(): void {
+    this.account.balance += this.amount;
+  }
+}
+
+class Income extends AccountCommand {
+  constructor(account: BankAccount, amount: number) {
+    super(account, amount, 'income');
+  }
+
+  execute(): void {
+    this.account.balance += this.amount;
+  }
+
+  undo(): void {
+    this.account.balance -= this.amount;
+  }
+}
+
+class BankAccount {
+  public name: string;
+  public balance: number;
+
+  constructor(name: string) {
+    this.name = name;
+    this.balance = 0;
+  }
+}
+
+class Bank {
+  private commands: AccountCommand[] = [];
+
+  operation(account: BankAccount, amount: number): void {
+    const Command = amount < 0 ? Withdraw : Income;
+    const command = new Command(account, Math.abs(amount));
+    command.execute();
+    this.commands.push(command);
+  }
+
+  undo(count: number): void {
+    for (let i = 0; i < count; i++) {
+      const command = this.commands.pop();
+      if (command) {
+        command.undo();
+      }
+    }
+  }
+
+  showOperations(): void {
+    const output = this.commands.map((command) => ({
+      operation: command.operation,
+      account: command.account.name,
+      amount: command.amount,
+    }));
+    console.table(output);
+  }
+}
+
+// Usage
+
+const bank = new Bank();
+const account1 = new BankAccount('Marcus Aurelius');
+bank.operation(account1, 1000);
+bank.operation(account1, -50);
+const account2 = new BankAccount('Antoninus Pius');
+bank.operation(account2, 500);
+bank.operation(account2, -100);
+bank.operation(account2, 150);
+bank.showOperations();
+console.table([account1, account2]);
+bank.undo(2);
+bank.showOperations();
+console.table([account1, account2]);

TypeScript/2-js-way.ts

@@ -0,0 +1,101 @@
+type Account = {
+  name: string;
+  balance: number;
+};
+
+const accounts = new Map<string, Account>();
+
+const addAccount = (name: string): Account => {
+  const account: Account = { name, balance: 0 };
+  accounts.set(name, account);
+  return account;
+};
+
+interface Command {
+  operation: string;
+  account: string;
+  amount: number;
+}
+
+type OperationType = 'withdraw' | 'income';
+
+const OPERATIONS: Record<OperationType, { 
+  execute: (command: Command) => void; 
+  undo: (command: Command) => void; 
+}> = {
+  withdraw: {
+    execute: (command: Command): void => {
+      const account = accounts.get(command.account);
+      if (account) {
+        account.balance -= command.amount;
+      }
+    },
+    undo: (command: Command): void => {
+      const account = accounts.get(command.account);
+      if (account) {
+        account.balance += command.amount;
+      }
+    },
+  },
+  income: {
+    execute: (command: Command): void => {
+      const account = accounts.get(command.account);
+      if (account) {
+        account.balance += command.amount;
+      }
+    },
+    undo: (command: Command): void => {
+      const account = accounts.get(command.account);
+      if (account) {
+        account.balance -= command.amount;
+      }
+    },
+  },
+};
+
+class Bank {
+  private commands: Command[] = [];
+
+  operation(account: Account, amount: number): void {
+    const operation = amount < 0 ? 'withdraw' : 'income';
+    const { execute } = OPERATIONS[operation];
+    const command: Command = {
+      operation,
+      account: account.name,
+      amount: Math.abs(amount),
+    };
+    this.commands.push(command);
+    execute(command);
+  }
+
+  undo(count: number): void {
+    for (let i = 0; i < count; i++) {
+      const command = this.commands.pop();
+      if (command) {
+        const operation = command.operation as OperationType;
+        const { undo } = OPERATIONS[operation];
+        undo(command);
+      }
+    }
+  }
+
+  showOperations(): void {
+    console.table(this.commands);
+  }
+}
+
+// Usage
+
+const bank = new Bank();
+const account1 = addAccount('Marcus Aurelius');
+bank.operation(account1, 1000);
+bank.operation(account1, -50);
+const account2 = addAccount('Antoninus Pius');
+bank.operation(account2, 500);
+bank.operation(account2, -100);
+bank.operation(account2, 150);
+bank.showOperations();
+console.table([account1, account2]);
+bank.undo(2);
+bank.showOperations();
+console.table([account1, account2]);