function Vehicle(type) {
  this.type = type;
  this.wheels = 4;
}

Vehicle.prototype.getInfo = function() {
  return `${this.type} with ${this.wheels} wheels`;
};

const car = new Vehicle('sedan');
const bike = Vehicle('motorcycle');

console.log(car.getInfo());
console.log(typeof bike);
console.log(bike?.type || 'undefined');

function* innerGenerator() {
  yield 1;
  yield 2;
  return 'inner-done';
}

function* outerGenerator() {
  yield 'start';
  const result = yield* innerGenerator();
  yield result;
  yield 'end';
}

const gen = outerGenerator();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);

function processData() {
  const results = [];
  
  for (let i = 0; i < 3; i++) {
    const multiplier = i + 1;
    
    setTimeout(() => {
      results.push(i * multiplier);
    }, 0);
  }
  
  setTimeout(() => {
    console.log(results.join(','));
  }, 10);
}

processData();

class Calculator {
  constructor(value) {
    this.value = value;
  }
  
  add(num) {
    this.value += num;
    return this;
  }
  
  multiply(num) {
    this.value *= num;
    return this;
  }
}

const calc = new Calculator(5);
const addMethod = calc.add;
const result = addMethod.call(calc, 3).multiply(2);
console.log(result.value);

class EventEmitter {
  constructor() {
    this.events = new Map();
  }
  
  on(event, callback) {
    if (!this.events.has(event)) {
      this.events.set(event, []);
    }
    this.events.get(event).push(callback);
    return this;
  }
  
  emit(event, ...args) {
    const callbacks = this.events.get(event);
    if (callbacks) {
      callbacks.forEach(cb => cb(...args));
    }
    return this;
  }
}

const emitter = new EventEmitter();
emitter.on('test', x => console.log(x * 2))
       .on('test', x => console.log(x + 10))
       .emit('test', 5);

const obj = {
  data: ['x', 'y', 'z'],
  *[Symbol.iterator]() {
    for (let i = this.data.length - 1; i >= 0; i--) {
      yield this.data[i].toUpperCase();
    }
  }
};

const result = [];
for (const item of obj) {
  result.push(item);
  if (result.length === 2) break;
}

console.log(result.join('-'));

const x = 15;
const y = 10;
const z = 3;

const result1 = x & y;
const result2 = x | y;
const result3 = x ^ y;
const result4 = ~x;
const result5 = y << z;
const result6 = y >> 1;

console.log(`${result1},${result2},${result3},${result4},${result5},${result6}`);

const wm = new WeakMap();
let obj1 = { name: 'John' };
let obj2 = { name: 'Jane' };

wm.set(obj1, 'developer');
wm.set(obj2, 'designer');

console.log(wm.get(obj1));
console.log(wm.has(obj2));

obj1 = null;
console.log(wm.get(obj1));

const normalObj = {};
try {
  wm.set('string', 'value');
} catch (e) {
  console.log('error');
}