Take a look at the following code:

1    let x = 1;
2    function f1()
3    {
4        let x = 2;
5        console.log(x);
6    }
7    console.log(x);

Explain why line 4 and line 6 output different numbers.

Answer : console.log inside the function takes the x which is declared inside the function. Local variable . console.log outside the function takes the x which is on line 1 because it is global.

Take a look at the following code:

let x = 10

function f1()
{
    console.log(x)
    let y = 20
}

console.log(f1())
console.log(y)

What will be the output of this code. Explain your answer in 50 words or less.

Answer: First console.log writes 10, second console.log return undefined because f1 function doesn't have any return, third console.log return is not defined because y is local variable inside f1 function.

Take a look at the following code:

const x = 9;

function f1(val) {
  val = val + 1;
  return val;
}

f1(x);
console.log(x);

const y = { x: 9 };

function f2(val) {
  val.x = val.x + 1;
  return val;
}

f2(y);
console.log(y);

What will be the output of this code. Explain your answer in 50 words or less.

Answer: First console.log writes 9, second console.log writes {x: 10 }.