Add JavaScript way

Author: tshemsedinov

JavaScript/6-js-way.js

@@ -0,0 +1,79 @@
+'use strict';
+
+const accounts = new Map();
+
+const addAccount = (name) => {
+  const account = { name, balance: 0 };
+  accounts.set(name, account);
+  return account;
+};
+
+const OPERATIONS = {
+  withdraw: {
+    execute: (command) => {
+      const account = accounts.get(command.account);
+      account.balance -= command.amount;
+    },
+    undo: (command) => {
+      const account = accounts.get(command.account);
+      account.balance += command.amount;
+    },
+  },
+  income: {
+    execute: (command) => {
+      const account = accounts.get(command.account);
+      account.balance += command.amount;
+    },
+    undo: (command) => {
+      const account = accounts.get(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 = {
+      operation,
+      account: account.name,
+      amount: 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;
+      const { undo } = OPERATIONS[operation];
+      undo(command);
+    }
+  }
+
+  showOperations() {
+    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]);