A simple bank-account FSM, implemented in javascript-state-machine

bank-account.js

const StateMachine = require('javascript-state-machine');

const Account = StateMachine.factory({
  init: 'open',
  transitions: [
    // open state
    {name: 'deposit', from: 'open', to: 'open'},
    {name: 'withdraw', from: 'open', to: 'open'},
    {name: 'available', from: 'open', to: 'open'},
    {name: 'placeHold', from: 'open', to: 'held'},
    {name: 'close', from: 'open', to: 'closed'},
    // held state
    {name: 'deposit', from: 'held', to: 'held'},
    {name: 'available', from: 'held', to: 'held'},
    {name: 'removeHold', from: 'held', to: 'open'},
    {name: 'close', from: 'held', to: 'closed'},
    // closed state
    {name: 'reopen', from: 'closed', to: 'open'},
  ],
  data: function(accountBalance) {
    return { accountBalance: accountBalance || 0 };
  },
  methods:{
    onDeposit: function(lc, amount) {
      if (amount < 0) {
        console.log(`ERROR: cannot deposit a negative amount`);
        return false;
      }
      this.accountBalance += amount;
    },
    onWithdraw: function(lc, amount) {
      if (this.accountBalance < amount) {
        console.log(`ERROR: ${amount} is more than you have in the account! Cannot withdraw this amount.`);
        return false;
      }
      this.accountBalance -= amount;
    },
    onInvalidTransition: function(event, from, to) {
      console.log(`ERROR: It's not possible to ${event} from an account that is ${from} `);
    },
    balance: function() {
      if (!this.can('available')) {
        console.log(`ERROR: cannot call available in ${this.state}`);
        return false;
      }
      return this.accountBalance;
    },
    statement: function () {
      console.log(`Account is ${this.state} with a balance of ${this.balance()}`)
    }
  }
});

const account = new Account(10);

// legal operations on an open account
account.statement();
account.deposit(5);
account.statement();
account.withdraw(10);
account.statement();
account.withdraw(10);
account.statement();

// moving states
account.placeHold();
account.statement();
account.removeHold();
account.close();
account.statement();
account.reopen();
account.statement();

// move state to test illegal operations
account.placeHold();
account.withdraw(1);
account.removeHold();
account.withdraw(1);
account.statement();

// Visualization also built in
const visualize = require('javascript-state-machine/lib/visualize');
const fs = require('fs');
const viz = require('viz.js');


const dot = visualize(account);
const svg = viz(dot, { format: "svg"});
fs.writeFileSync('./account.svg', svg, 'utf8');
fs.writeFileSync('./account.dot', dot, 'utf8');