function removeOdd(arr){
  //remove odd number of arr
  for (var i=arr.length;i>=0;i--)
    if (arr[i]%2) arr.splice(i,1)
  return arr;
}
console.log(removeOdd([1,2,3,4,5]))   
console.log(removeOdd([1,3,5,7,9]))

let person = {
  name: 'Alice',
  age: 30,
  valueOf: function() {
    return this.age;
  }
};

let result = person + 10;
console.log(result);

var a=[1,2,3,4,5];
console.log(a.some(x=>x>4)); 
console.log(a.some(x=>x>5));

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

const result = numbers
  .filter(num => num % 2 === 0)
  .map(num => num * num)
  .reduce((acc, num) => acc + num, 0);

console.log(result);

let x = { 
   a: 1,
   b: 2
};
let y = {
   b: 3,
   c: 4
};
Object.setPrototypeof(x, y);
console.log(x.b);

var arr1=[1,2,3,4,5]
arr1.reverse()
console.log(arr1)   
var arr2=['a','b','c']
arr2.reverse()
console.log(arr2)

const sym1 = Symbol('description');
const sym2 = Symbol('description');

const obj = {
  [sym1]: 'value1',
  [sym2]: 'value2'
};

console.log(obj[sym1]);

var x = 1;
function changeX() { x = 2; }
changeX();
console.log(x);

❓Что будет на выходе?

const array = [1, 2, 3, 4];
const result = array.reduceRight((acc, val) => acc - val);

console.log(result);

❓Что будет на выходе?

const weakMap = new WeakMap();
const array = [1, 2, 3];
const obj = {};

weakMap.set(obj, array);

const result = weakMap.get(obj).reduce((acc, val) => acc + val);

console.log(result);

function trickyScope() {
  var x = 10;
  if (true) {
    let x = 5;
    console.log(x);
  }
  console.log(x);
}

trickyScope();

const string = "JavaScript test";
const result = string.replace(/l/g, "");
console.log(result);

❓Что будет на выходе?

const obj = Object.freeze({
  a: [1, 2, 3],
  b: {
    c: 4
  }
});

obj.a.push(obj.b);
obj.b.c = 5;

console.log(obj.a);
console.log(obj.b.c);

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 trickyScope() {
  var a = 10;
  let b = 20;
  const c = 30;

  if (true) {
    var a = 40;
    let b = 50;
    const c = 60;
    console.log(a, b, c);
  }

  console.log(a, b, c);
}

trickyScope();

function trickyFunction(num) {  
  let result = 0;  
  for (let i = 0; i < num; i++) {  
    result += i;  
    if (i % 2 === 0) {  
      result *= 2;  
    } else {  
      result -= 1;  
    }  
  }  
  return result;  
}  
console.log(trickyFunction(4));

class School {
  constructor() {
    this.value = 255;
  }
}

console.log(School);

console.log(16);
setTimeout(() => console.log(20), 0);
Promise.resolve()
  .then(() => {
    console.log(18);
    return Promise.resolve(19);
  })
  .then(console.log);
console.log(17);

function trickyScope() {
    let x = 10;
    if (true) {
        let x = 20;
        console.log(x); // A
    }
    console.log(x); // B
    {
        let x = 30;
        console.log(x); // C
    }
    console.log(x); // D
}

trickyScope();

const string = "abc";
const digit = "16";
const arr = [...string, ...digit];
console.log(arr);

const obj = {
  a: 10,
  b: 20
};

with (obj) {
  var result = a + b;
}

console.log(result - obj.a == obj.b);