Which of the following is correct about variable scope in JavaScript?

What will be the output of the following code?

var a = 1; { var a = 2; } console.log(a);

A). 1

B). 2

C). undefined

D). ReferenceError

Which of the following is a valid variable name in JavaScript?

A). 2name

B). _name

C). #name

D).

What is the difference between let and var?

A). let is function-scoped, var is block-scoped

B). let is block-scoped, var is function-scoped

C). Both are block-scoped

D). Both are function-scoped

Which keyword should be used to declare a block-scoped variable?

A). var

B). let

C). const

D). Both let and const

Which of the following will cause an error?

A). let a = 10; a = 20;

B). const a = 10; a = 20;

C). var a = 10; a = 20;

D). None of the above

What will be the output of the following code?

const a = 10; a = 20; console.log(a);

A). 10

B). 20

C). Error

D). undefined

Which keyword is used to declare a variable in JavaScript?

A). var

B). let

C). const

D). All of the above

Which of the following is NOT a valid variable name in JavaScript?

A). myVar

B). $myVar

C). _myVar

D). 123myVar

What will be the output of the following code?

var x = 5; var y = 6; var z = x + y;

A). 11

B). 11

C). 5

D). 6

What will be the output of the following code?

let a = 1; let b = 2; let c = a + b; console.log(c);

A). 12

B). 12

C). 3

D). NaN