JavaScript test

let symbol1 = Symbol('description');
let symbol2 = Symbol('description');

const obj = {
  [symbol1]: 'value1',
  [symbol2]: 'value2'
};

console.log(obj[symbol1]);
console.log(symbol1 === symbol2);

function foo() {
   return typeof arguments;
};
console.log(foo(1, 2, 3));

function Person(name) {
  this.name = name;
  this.sayName = () => console.log(this.name);
}

const person1 = new Person('David');
const person2 = { name: 'Not David', sayName: person1.sayName };

person2.sayName();

const a = [1, 2, 3];
const b = a.slice(0, 2).push(4);
console.log(b);

async function processValues() {
  try {
    console.log('Start');
    const a = await Promise.resolve('First');
    console.log(a);
    const b = await Promise.reject('Error');
    console.log(b);
    return 'Done';
  } catch (err) {
    console.log(err);
    return 'Recovered';
  } finally {
    console.log('Finally');
  }
}

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

const obj = {
  name: 'Taylor',
  greet() {
    return `Hello, ${this.name}!`;
  },
  delayedGreet() {
    setTimeout(function() {
      console.log(this.greet());
    }, 100);
  }
};

obj.delayedGreet();

const a = { value: 1 };
const b = Object.create(a);
b.value = 2;

console.log(b.value);
console.log(a.value);

const obj = {
  name: 'Calculator',
  values: [1, 2, 3, 4, 5],
  
  regular: function() {
    return this.values.filter(function(x) {
      return x > 2;
    }).length;
  },
  
  arrow: function() {
    return this.values.filter(x => x > 2).length;
  },
  
  broken: () => {
    return this.values.filter(x => x > 2).length;
  }
};

console.log(obj.regular());
console.log(obj.arrow());
try {
  console.log(obj.broken());
} catch(e) {
  console.log('Error');
}

async function processValues() {
  try {
    console.log('Start');
    const a = await Promise.resolve('First');
    console.log(a);
    const b = await Promise.reject('Error');
    console.log(b);
    return 'Done';
  } catch (err) {
    console.log(err);
    return 'Recovered';
  } finally {
    console.log('Finally');
  }
}

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

console.log('1');

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

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

setTimeout(() => console.log('4'), 0);

Promise.resolve().then(() => {
  console.log('5');
  return Promise.resolve();
}).then(() => console.log('6'));

console.log('7');

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

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

const transform = pipe(
  add(5),
  multiply(3),
  subtract(2)
);

console.log(transform(4));
console.log(transform(0));

function main({ x, y } = { x: 1, y: 2 }) {
   console.log(x, y);
}

main({ x: 5 });

const obj = { a: 1, b: 2, c: 3 };
const result = Object.values(obj).reduce((acc, curr) => acc * curr, 1);
console.log(result);

async function foo() {
  console.log('Start');
  await Promise.resolve().then(() => {
    console.log('Inside Promise');
  });
  console.log('End');
}

foo();
console.log('Outside');

const data = { a: 1, b: 2, c: 3 };
const { a, ...rest } = data;
const newObj = { ...rest, a, d: 4 };

const arr = [1, 2, 3, 4, 5];
const [first, , third, ...remaining] = arr;
const result = [...remaining, third, first];

console.log(newObj);
console.log(result);

async function processData() {
  const promise1 = Promise.resolve('first');
  const promise2 = Promise.reject('error');
  const promise3 = Promise.resolve('third');
  
  try {
    const result = await Promise.allSettled([promise1, promise2, promise3]);
    console.log(result[0].status);
    console.log(result[1].reason);
    console.log(result[2].value);
  } catch (error) {
    console.log('caught:', error);
  }
}

processData();

const data = [
  { type: 'income', amount: 1000, category: 'salary' },
  { type: 'expense', amount: 200, category: 'food' },
  { type: 'income', amount: 500, category: 'freelance' },
  { type: 'expense', amount: 150, category: 'transport' }
];

const result = data.reduce((acc, item) => {
  const key = item.type;
  acc[key] = (acc[key] || 0) + item.amount;
  return acc;
}, {});

console.log(result.income - result.expense);

async function processValues() {
  try {
    console.log('Start');
    const a = await Promise.resolve('First');
    console.log(a);
    const b = await Promise.reject('Error');
    console.log(b);
    return 'Done';
  } catch (err) {
    console.log(err);
    return 'Recovered';
  } finally {
    console.log('Finally');
  }
}

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

const array = [1, 2, [3, 4, [5, 6]]];
const result = array.flat(2).map(n => n * 2);

console.log(result);