function* generator1() {
  yield 1;
  yield 2;
}

function* generator2() {
  yield* generator1();
  yield 3;
}

const gen = generator2();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);

const promise1 = Promise.resolve('first');
const promise2 = new Promise(resolve => {
  resolve('second');
});

const promise3 = Promise.resolve().then(() => 'third');

async function test() {
  console.log('start');
  
  const result1 = await promise1;
  console.log(result1);
  
  const result2 = await promise2;
  console.log(result2);
  
  const result3 = await promise3;
  console.log(result3);
  
  console.log('end');
}

test();

function Foo() {
  this.bar = 1;
}

Foo.prototype.bar = 2;

const foo = new Foo();
console.log(foo.bar);

function* gen() {
  yield 1;
  yield 2;
  yield 3;
}

async function asyncFunc() {
  for (let value of gen()) {
    await new Promise(res => setTimeout(res, 100));
    console.log(value);
  }
  return 'done';
}

const result = asyncFunc();
console.log(result instanceof Promise);

const asyncFunction = async () => {
  const delay = (ms) => new Promise(resolve => setTimeout(resolve, ms));

  const result = await Promise.race([delay(100), delay(500)]);
  return result;
};

asyncFunction().then(value => console.log(value));

const string = "“abc123def456ghi789";

const matches =
string.match(/\d+/g);
console. log(matches );

const numbers = [1, 2, 3, 4, 5];

const pipeline = (...fns) => (value) => fns.reduce((acc, fn) => fn(acc), value);

const multiply = (x) => (y) => x * y;
const add = (x) => (y) => x + y;
const square = (x) => x * x;

const transform = pipeline(
  multiply(2),
  add(3),
  square
);

const result = numbers.map(transform);
console.log(result);

const numbers = [1, 2, 3, 4, 5];

const pipeline = (...fns) => (value) => fns.reduce((acc, fn) => fn(acc), value);

const multiply = (x) => (y) => x * y;
const add = (x) => (y) => x + y;
const square = (x) => x * x;

const transform = pipeline(
  multiply(2),
  add(3),
  square
);

const result = numbers.map(transform);
console.log(result);

class Calculator {
  static multiply(a, b) {
    return a * b;
  }
  
  static add = (a, b) => {
    return a + b;
  }
}

class ScientificCalculator extends Calculator {
  static multiply(a, b) {
    return super.multiply(a, b) * 2;
  }
}

console.log(Calculator.multiply(3, 4));
console.log(ScientificCalculator.add(5, 6));
console.log(ScientificCalculator.multiply(2, 3));

class CustomError extends Error {
  constructor(message) {
    super(message);
    this.name = 'CustomError';
  }
}

try {
  try {
    throw new CustomError('inner error');
  } catch (e) {
    console.log(e.name);
    throw new Error('outer error');
  }
} catch (e) {
  console.log(e.message);
  console.log(e instanceof CustomError);
}

class Calculator {
  static multiply(a, b) {
    return a * b;
  }
  
  static add = (a, b) => {
    return a + b;
  }
}

class ScientificCalculator extends Calculator {
  static multiply(a, b) {
    return super.multiply(a, b) * 2;
  }
}

console.log(Calculator.multiply(3, 4));
console.log(ScientificCalculator.add(5, 6));
console.log(ScientificCalculator.multiply(2, 3));

const obj = {
  name: 'Sarah',
  regularMethod: function() {
    return () => {
      console.log(this.name);
    };
  },
  arrowMethod: () => {
    return () => {
      console.log(this.name);
    };
  }
};

const regular = obj.regularMethod();
const arrow = obj.arrowMethod();
regular();
arrow();

const numbers = [1, 2, 3, 4, 5];

const result = numbers
  .map(x => x * 2)
  .filter(x => x > 5)
  .reduce((acc, x) => {
    acc.push(x.toString());
    return acc;
  }, [])
  .map(x => x + '!')
  .join(' | ');

console.log(result);
console.log(typeof result);

class LightMachine {
  constructor() {
    this.states = {
      green: { next: 'yellow' },
      yellow: { next: 'red' },
      red: { next: 'green' }
    };
    this.currentState = 'green';
  }

  transition() {
    this.currentState = this.states[this.currentState].next;
    return this.currentState;
  }
}

const lightMachine = new LightMachine();
let result = '';
for (let i = 0; i < 5; i++) {
  result += lightMachine.transition() + ' ';
}
console.log(result.trim());

const data = '{"name": "Maria", "age": 25, "skills": ["JavaScript", "Python"]}';

try {
  const parsed = JSON.parse(data);
  const modified = {
    ...parsed,
    age: parsed.age + 5,
    skills: [...parsed.skills, "TypeScript"]
  };
  
  const serialized = JSON.stringify(modified, null, 0);
  const reparsed = JSON.parse(serialized);
  
  console.log(reparsed.skills.length);
  console.log(typeof reparsed.age);
} catch (error) {
  console.log('Parse error');
}

const str = 'JavaScript';
const result1 = str.slice(-6, -2);
const result2 = str.substring(-6, -2);
const result3 = str.substr(-6, 4);
const combined = [result1, result2, result3];
const final = combined.map(s => s || 'empty').join(' | ');
console.log(final);

class Observable {
  constructor(subscribe) {
    this.subscribe = subscribe;
  }
  
  map(fn) {
    return new Observable(observer => {
      return this.subscribe({
        next: value => observer.next(fn(value)),
        error: err => observer.error(err),
        complete: () => observer.complete()
      });
    });
  }
}

const source = new Observable(observer => {
  observer.next(1);
  observer.next(2);
  observer.complete();
});

const doubled = source.map(x => x * 2);
doubled.subscribe({
  next: value => console.log(value),
  complete: () => console.log('done')
});

const original = {
  name: 'Sarah',
  scores: [85, 92, 78],
  details: {
    age: 25,
    city: 'Portland'
  }
};

const copy1 = { ...original };
const copy2 = JSON.parse(JSON.stringify(original));

copy1.name = 'Emma';
copy1.scores.push(95);
copy1.details.age = 30;

console.log(original.name, original.scores.length, original.details.age);