class StateMachine {
  constructor() {
    this.state = 'idle';
    this.transitions = {
      idle: { start: 'running' },
      running: { pause: 'paused', stop: 'idle' },
      paused: { resume: 'running', stop: 'idle' }
    };
  }
  
  transition(action) {
    const validTransitions = this.transitions[this.state];
    if (validTransitions && validTransitions[action]) {
      this.state = validTransitions[action];
      return true;
    }
    return false;
  }
}

const machine = new StateMachine();
console.log(machine.transition('pause'));
console.log(machine.state);
console.log(machine.transition('start'));
console.log(machine.state);

const userInput = "<script>alert('xss')</script>";
const sanitized = userInput.replace(/<script[^>]*>.*?<\/script>/gi, '');

const users = new Map();
users.set('admin', { password: 'secret123', role: 'admin' });
users.set('guest', { password: 'guest', role: 'user' });

function authenticate(username, password) {
  const user = users.get(username);
  return user && user.password === password ? user.role : null;
}

const role1 = authenticate('admin', 'secret123');
const role2 = authenticate('guest', 'wrong');
const role3 = authenticate('hacker', 'secret123');

console.log(sanitized);
console.log(role1, role2, role3);

const obj = {
  name: 'Sarah',
  getName() { return this.name; },
  getNameArrow: () => this.name
};

const { getName, getNameArrow } = obj;
const boundGetName = obj.getName.bind(obj);

console.log(getName());
console.log(getNameArrow());
console.log(boundGetName());
console.log(obj.getName());
console.log(obj.getNameArrow());

function processData() {
  try {
    console.log('start');
    throw new Error('oops');
    console.log('after throw');
  } catch (e) {
    console.log('catch');
    return 'caught';
  } finally {
    console.log('finally');
  }
  console.log('end');
}

const result = processData();
console.log(result);

function highlight(strings, ...values) {
  return strings.reduce((result, string, i) => {
    const value = values[i] ? `<mark>${values[i]}</mark>` : '';
    return result + string + value;
  }, '');
}

const name = 'Sarah';
const age = 25;
const template = highlight`Hello ${name}, you are ${age} years old!`;
console.log(template);

const empty = highlight`No interpolation here`;
console.log(empty);