25 MCQs of JavaScript | SET - 5

In this article, I have listed 25 javascript MCQs for you to practice. Comment your answer with proper justification.

Table of contents

• Q1

• Q2

• Q3

• Q4

• Q5

• Q6

• Q7

• Q8

• Q9 - What does this method do?

• Q10

• Q12

• Q13

• Q14

• Q15 - Which method(s) will return the value 'Hello world!'?

• Q16

• Q17

• Q18

• Q19

• Q20

• Q21

• Q22

• Q23

• Q24

• Q25

• Thank You ❤️

Q1

const myPromise = () => Promise.resolve('I have resolved!');

function firstFunction() {
  myPromise().then(res => console.log(res));
  console.log('second');
}

async function secondFunction() {
  console.log(await myPromise());
  console.log('second');
}

firstFunction();
secondFunction();

Q2

const set = new Set();

set.add(1);
set.add('Lydia');
set.add({ name: 'Lydia' });

for (let item of set) {
  console.log(item + 2);
}

Q3

Promise.resolve(5);

Q4

function compareMembers(person1, person2 = person) {
  if (person1 !== person2) {
    console.log('Not the same!');
  } else {
    console.log('They are the same!');
  }
}

const person = { name: 'Lydia' };

compareMembers(person);

Q5

const colorConfig = {
  red: true,
  blue: false,
  green: true,
  black: true,
  yellow: false,
};

const colors = ['pink', 'red', 'blue'];

console.log(colorConfig.colors[1]);

Q6

console.log('❤️' === '❤️');

Q7

const emojis = ['✨', '🥑', '😍'];

emojis.map(x => x + '✨');
emojis.filter(x => x !== '🥑');
emojis.find(x => x !== '🥑');
emojis.reduce((acc, cur) => acc + '✨');
emojis.slice(1, 2, '✨');
emojis.splice(1, 2, '✨');

Q8

const food = ['🍕', '🍫', '🥑', '🍔'];
const info = { favoriteFood: food[0] };

info.favoriteFood = '🍝';

console.log(food);

Q9 - What does this method do?

JSON.parse();

Q10

let name = 'Lydia';

function getName() {
  console.log(name);
  let name = 'Sarah';
}

getName();

Q12

function* generatorOne() {
  yield ['a', 'b', 'c'];
}

function* generatorTwo() {
  yield* ['a', 'b', 'c'];
}

const one = generatorOne();
const two = generatorTwo();

console.log(one.next().value);
console.log(two.next().value);

Q13

console.log(`${(x => x)('I love')} to program`);

Q14

let config = {
  alert: setInterval(() => {
    console.log('Alert!');
  }, 1000),
};

config = null;

Q15 - Which method(s) will return the value 'Hello world!'?

const myMap = new Map();
const myFunc = () => 'greeting';

myMap.set(myFunc, 'Hello world!');

//1
myMap.get('greeting');
//2
myMap.get(myFunc);
//3
myMap.get(() => 'greeting');

Q16

const person = {
  name: 'Lydia',
  age: 21,
};

const changeAge = (x = { ...person }) => (x.age += 1);
const changeAgeAndName = (x = { ...person }) => {
  x.age += 1;
  x.name = 'Sarah';
};

changeAge(person);
changeAgeAndName();

console.log(person);

Q17

function sumValues(x, y, z) {
  return x + y + z;
}

Q18

let num = 1;
const list = ['🥳', '🤠', '🥰', '🤪'];

console.log(list[(num += 1)]);

Q19

const person = {
  firstName: 'Lydia',
  lastName: 'Hallie',
  pet: {
    name: 'Mara',
    breed: 'Dutch Tulip Hound',
  },
  getFullName() {
    return `${this.firstName} ${this.lastName}`;
  },
};

console.log(person.pet?.name);
console.log(person.pet?.family?.name);
console.log(person.getFullName?.());
console.log(member.getLastName?.());

Q20

const groceries = ['banana', 'apple', 'peanuts'];

if (groceries.indexOf('banana')) {
  console.log('We have to buy bananas!');
} else {
  console.log(`We don't have to buy bananas!`);
}

Q21

const config = {
  languages: [],
  set language(lang) {
    return this.languages.push(lang);
  },
};

console.log(config.language);

Q22

const name = 'Lydia Hallie';

console.log(!typeof name === 'object');
console.log(!typeof name === 'string');

Q23

const add = x => y => z => {
  console.log(x, y, z);
  return x + y + z;
};

add(4)(5)(6);

Q24

async function* range(start, end) {
  for (let i = start; i <= end; i++) {
    yield Promise.resolve(i);
  }
}

(async () => {
  const gen = range(1, 3);
  for await (const item of gen) {
    console.log(item);
  }
})();

Q25

const myFunc = ({ x, y, z }) => {
  console.log(x, y, z);
};

myFunc(1, 2, 3);

Thank You ❤️