const arr = [1, 2, 3, 4, 5];
const result = arr
  .map(x => x * 2)
  .filter(x => x > 5)
  .reduce((acc, val) => {
    return acc + (val % 3 === 0 ? val : 0);
  }, 0);

console.log(result);

console.log('Start');

setTimeout(() => {
  console.log('Timeout 1');
}, 0);

Promise.resolve().then(() => {
  console.log('Promise 1');
}).then(() => {
  console.log('Promise 2');
});

setTimeout(() => {
  console.log('Timeout 2');
}, 0);

console.log('End');

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

const sm = new StateMachine();
console.log(sm.transition('start'));
console.log(sm.state);
console.log(sm.transition('reset'));
console.log(sm.state);

const target = { name: 'Sarah', age: 25 };
const handler = {
  get(obj, prop) {
    if (prop === 'toString') {
      return () => `Person: ${obj.name}`;
    }
    return Reflect.get(obj, prop);
  },
  has(obj, prop) {
    return prop !== 'age' && Reflect.has(obj, prop);
  }
};
const proxy = new Proxy(target, handler);
console.log(proxy.name);
console.log('age' in proxy);
console.log(proxy.toString());

const numbers = [1, 2, 3, 4, 5, 6];

const result = numbers.reduce((acc, num) => {
  if (num % 2 === 0) {
    acc.even += num;
  } else {
    acc.odd *= num;
  }
  return acc;
}, { even: 1, odd: 1 });

console.log(result);

const matrix = [
  [1, 2, 3],
  [4, 5, 6],
  [7, 8, 9],
];

let columnSums = [];

for (let i = 0; i < matrix[0].length; i++) {
  let sum = 0;
  for (let j = 0; j < matrix.length; j++) {
    sum += matrix[i][i];
  }
  columnSums.push(sum);
}
console.log(columnSums);

const arr = [1, 2, 3];
const str = arr.join([4]);
console.log(typeof str);
console.log(str);

var arr = Array.from({ length: 5 }, (v, i) => i * 2);
console.log(arr);

function main() {
  console.log(1);
  
  setTimeout(() => console.log(2), 0);
  
  Promise.resolve().then(() => {
    console.log(3);
    setTimeout(() => console.log(4), 0);
  }).then(() => console.log(5));
  
  Promise.resolve().then(() => console.log(6));
  
  console.log(7);
}

main();

const cache = new WeakMap();
const obj1 = { id: 1 };
const obj2 = { id: 2 };

cache.set(obj1, 'data1');
cache.set(obj2, 'data2');

obj2.newProp = 'test';

console.log(cache.has(obj1), cache.has(obj2), cache.has({ id: 1 }));

const obj = { length: 3 };
console.log(Object.keys(obj).length);

console.log('1');

Promise.resolve().then(() => {
  console.log('2');
  Promise.resolve().then(() => console.log('3'));
});

Promise.resolve().then(() => {
  console.log('4');
});

setTimeout(() => console.log('5'), 0);

console.log('6');

var str="good wood food cat bat hat";
console.log( str.match(/((g|w|f)ood)|((c|b|h)at)/g) );

const str = "a 1 b 2 c 3 d 04";

function foo(str) {
   const regex = /\d+/g;
   const matches = str.match(regex);
   return matches.lenght;
}

const obj = {};
let value = 0;

Object.defineProperty(obj, 'prop', {
  get() {
    return value;
  },
  set(newValue) {
    value = newValue + 1;
  },
  configurable: true,
  enumerable: true
});

obj.prop = 10;
console.log(obj.prop);

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 );

var a = 0, b = 0, arr = [3, 6, 9, 6, 9, 3];
var data = arr.some((x, i)=>{
  a = arr[i]; 
  b = arr[i + 1];
  return a + b == 15
})
console.log(data)
console.log(a, b)

const array = [1, 2, 3, 4, 5];
const result = array.map(function(n) {
  return this ? n : 1 * 2 + 3;
}, false);

console.log([...result, ...result]);

class DataProcessor {
  constructor(value) {
    this.value = value;
  }
  
  transform(fn) {
    return new DataProcessor(fn(this.value));
  }
  
  getValue() {
    return this.value;
  }
}

const multiply = x => x * 2;
const add = x => x + 10;
const square = x => x * x;

const result = new DataProcessor(5)
  .transform(multiply)
  .transform(add)
  .transform(square)
  .getValue();

console.log(result);