Hello Frontend Team,
Join this discussion group and feel free to ask any doubts or any ' how to do in frontend ' related queries so that I can help 🙂🫡✌️

https://t.me/+I5O_KN1SZJM4YWNl

What will be the ouptut of this function?

function sayHi() {
console.log(name);
console.log(age);
var name = 'Lydia';
let age = 21;
}

sayHi();

A: Lydia and undefined
B: Lydia and ReferenceError
C: ReferenceError and 21
D: undefined and ReferenceError

// 2. Problem Solving

What will be the output ?

for (var i = 0; i < 3; i++) {
setTimeout(() => console.log(i), 1);
}

for (let i = 0; i < 3; i++) {
setTimeout(() => console.log(i), 1);
}

A: 0 1 2 and 0 1 2
B: 0 1 2 and 3 3 3
C: 3 3 3 and 0 1 2

Explained Answer will be posted Tomorrow EOD ✌️

Answer: C
Because of the event queue in JavaScript, the setTimeout callback function is called after the loop has been executed. Since the variable i in the first loop was declared using the var keyword, this value was global. During the loop, we incremented the value of i by 1 each time, using the unary operator ++. By the time the setTimeout callback function was invoked, i was equal to 3 in the first example.
In the second loop, the variable i was declared using the let keyword: variables declared with the let (and const) keyword are block-scoped (a block is anything between { }). During each iteration, i will have a new value, and each value is scoped inside the loop.

// 3. Problem Solving

What's the output?

const shape = {
radius: 10,
diameter() {
return this.radius * 2;
},
perimeter: () => 2 * Math.PI * this.radius,
};

console.log(shape.diameter());
console.log(shape.perimeter());

A: 20 and 62.83185307179586
B: 20 and NaN
C: 20 and 63
D: NaN and 63

Did you read this???

https://thedailyfrontend.com/learn-frontend-by-cloning-these-5-websites/

Learn Frontend by cloning these 5 websites

Answer: B

20 and NaN

Note that the value of diameter is a regular function, whereas the value of perimeter is an arrow function.
With arrow functions, the this keyword refers to its current surrounding scope, unlike regular functions! This means that when we call perimeter, it doesn't refer to the shape object, but to its surrounding scope (window for example).
There is no value radius on that object, which returns NaN.