function recursivePascalTriangle(n, row = [1], triangle = []) {
  triangle.push(row);
  if (n === triangle.length) {
    return triangle;
  }
  const nextRow = [1];
  for (let i = 1; i < row.length; i++) {
    nextRow.push(row[i] + row[i - 1]);
  }
  nextRow.push(1);
  return recursivePascalTriangle(n, nextRow, triangle);
}

const result = recursivePascalTriangle(5);

console.log(result);

const user = {
  profile: {
    name: 'Alice',
    settings: {
      notifications: {
        email: true,
        sms: false
      }
    }
  },
  getPreference(type) {
    return this.profile?.settings?.notifications?.[type] ?? 'not configured';
  }
};

const admin = {
  profile: {
    name: 'Admin',
    settings: null
  },
  getPreference: user.getPreference
};

console.log(admin.getPreference('email'));

function processConfig(config) {
  const cache = config.cache ?? true;
  const timeout = config.timeout ?? 1000;
  const retries = config.retries ?? 3;
  
  return {
    useCache: cache,
    timeoutMs: timeout,
    maxRetries: retries
  };
}

const result = processConfig({ timeout: 0, retries: false });
console.log(result);

const arr = [];
arr.length = 3;
arr[10] = 7;
arr.forEach((el, i) => console.log(i))

'use strict';

function strictModeExample() {
  undeclaredVariable = 10;
  try {
    console.log(undeclaredVariable);
  } catch (e) {
    console.log('Error:', e.message);
  }
}

strictModeExample();

function trickyArgs(a, b, c) {
  arguments[0] = 10;
  arguments[1] = 20;
  arguments[2] = 30;
  console.log(a + b + c);
}
trickyArgs(1, 2, 3);

const array = Array.from({ length: 5 }, () => Math.random() > 0.5);

console.log(array);

function capIt(str){
  return str.split(/ /)
            .map(s=>s.replace(/^./,x=>x.toUpperCase()))
            .join(" ")
}
console.log( capIt("hello world!"))  
console.log( capIt("my name is John."))

async function asyncChain() {
   const values = [2, 3, 5, 7, 0];
   const total = await values.reduce(async (acc, values) => {
      const current = await acc;
      return current * values;
   }, Promise.resolve(1));
   return total;
}

asyncChain().then(result => console.log(result));

function Person(name) {
  this.name = name;
}
Person.prototype.greet = function() {
  return `Hello, my name is ${this.name}`;
};
const john = new Person('John');
console.log(john.greet());

const target = { a: 1, b: 2 };
const handler = {
  get(obj, prop) {
    return prop === 'sum' ? obj.a + obj.b : Reflect.get(obj, prop);
  },
  set(obj, prop, value) {
    if (prop === 'a' && value < 0) {
      return false;
    }
    return Reflect.set(obj, prop, value);
  }
};

const proxy = new Proxy(target, handler);
proxy.a = -5;
proxy.b = 10;
console.log(`${proxy.a}, ${proxy.b}, ${proxy.sum}`);

async function test() {
  console.log('1');
  
  setTimeout(() => {
    console.log('2');
  }, 0);
  
  await Promise.resolve();
  console.log('3');
  
  new Promise(resolve => {
    console.log('4');
    resolve();
  }).then(() => {
    console.log('5');
  });
  
  console.log('6');
}

test();
console.log('7');

function multiply(a, b) {
  if (b === 0) {
    return 0;
  } else if (b > 0) {
    return a + multiply(a, b - 1);
  } else {
    return -multiply(a, -b);
  }
}

console.log(multiply(-7, -5));