Add undo for anemic command

Author: tshemsedinov

JavaScript/5-undo.js

@@ -0,0 +1,87 @@
+'use strict';
+
+class AccountCommand {
+  constructor(operation, account, amount) {
+    this.operation = operation;
+    this.account = account;
+    this.amount = amount;
+  }
+}
+
+class BankAccount {
+  constructor(name) {
+    this.name = name;
+    this.balance = 0;
+    BankAccount.collection.set(name, this);
+  }
+  static find(name) {
+    return BankAccount.collection.get(name);
+  }
+}
+
+BankAccount.collection = new Map();
+
+const operations = {
+  Withdraw: {
+    execute: command => {
+      const account = BankAccount.find(command.account);
+      account.balance -= command.amount;
+    },
+    undo: command => {
+      const account = BankAccount.find(command.account);
+      account.balance += command.amount;
+    },
+  },
+  Income: {
+    execute: command => {
+      const account = BankAccount.find(command.account);
+      account.balance += command.amount;
+    },
+    undo: command => {
+      const account = BankAccount.find(command.account);
+      account.balance -= command.amount;
+    },
+  },
+};
+
+class Bank {
+  constructor() {
+    this.commands = [];
+  }
+  operation(account, amount) {
+    const operation = amount < 0 ? 'Withdraw' : 'Income';
+    const { execute } = operations[operation];
+    const command = new AccountCommand(
+      operation, account.name, Math.abs(amount)
+    );
+    this.commands.push(command);
+    execute(command);
+  }
+  undo(count) {
+    for (let i = 0; i < count; i++) {
+      const command = this.commands.pop();
+      const operation = command.amount < 0 ? 'Withdraw' : 'Income';
+      const { undo } = operations[operation];
+      undo(command);
+    }
+  }
+  showOperations() {
+    console.table(this.commands);
+  }
+}
+
+// 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]);