Engineer bro!
Wed Nov 17 2021 (2 years ago)
Engineer by mistake!
I am a software engineer by passion
In this article, I have listed 25 javascript MCQs for you to practice. Comment your answer with proper justification.
Q5 - When you click the paragraph, what's the logged output?
Q15 - What does the setInterval method return in the browser?
String.prototype.giveLydiaPizza = () => {
return 'Just give Lydia pizza already!';
};
const name = 'Lydia';
console.log(name.giveLydiaPizza())
const a = {};
const b = { key: 'b' };
const c = { key: 'c' };
a[b] = 123;
a[c] = 456;
console.log(a[b]);
const foo = () => console.log('First');
const bar = () => setTimeout(() => console.log('Second'));
const baz = () => console.log('Third');
bar();
foo();
baz();
<div onclick="console.log('first div')">
<div onclick="console.log('second div')">
<button onclick="console.log('button')">
Click!
</button>
</div>
</div>
<div onclick="console.log('div')">
<p onclick="console.log('p')">
Click here!
</p>
</div>
const person = { name: 'Lydia' };
function sayHi(age) {
return `${this.name} is ${age}`;
}
console.log(sayHi.call(person, 21));
console.log(sayHi.bind(person, 21));
function sayHi() {
return (() => 0)();
}
console.log(typeof sayHi());
0;
new Number(0);
('');
(' ');
new Boolean(false);
undefined;
console.log(typeof typeof 1);
const numbers = [1, 2, 3];
numbers[10] = 11;
console.log(numbers);
(() => {
let x, y;
try {
throw new Error();
} catch (x) {
(x = 1), (y = 2);
console.log(x);
}
console.log(x);
console.log(y);
})();
A: primitive or object
B: function or object
C: trick question! only objects
D: number or object
let and = [[0, 1], [2, 3]].reduce(
(acc, cur) => {
return acc.concat(cur);
},
[1, 2],
);
console.log(ans)
!!null;
!!'';
!!1;
setInterval(() => console.log('Hi'), 1000);
console.log([...'Lydia']);
function* generator(i) {
yield i;
yield i * 2;
}
const gen = generator(10);
console.log(gen.next().value);
console.log(gen.next().value);
const firstPromise = new Promise((res, rej) => {
setTimeout(res, 500, 'one');
});
const secondPromise = new Promise((res, rej) => {
setTimeout(res, 100, 'two');
});
const ans = Promise.race([firstPromise, secondPromise]).then(res => console.log(res));
console.log(ans)
let person = { name: 'Lydia' };
const members = [person];
person = null;
console.log(members);
const person = {
name: 'Lydia',
age: 21,
};
for (const item in person) {
console.log(item);
}
console.log(3 + 4 + '5');
const num = parseInt('7*6', 10);
console.log(num)
let ans = [1, 2, 3].map(num => {
if (typeof num === 'number') return;
return num * 2;
});
console.log(ans)
function getInfo(member, year) {
member.name = 'Lydia';
year = '1998';
}
const person = { name: 'Sarah' };
const birthYear = '1997';
getInfo(person, birthYear);
console.log(person, birthYear);
function greeting() {
throw 'Hello world!';
}
function sayHi() {
try {
const data = greeting();
console.log('It worked!', data);
} catch (e) {
console.log('Oh no an error:', e);
}
}
sayHi();
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