What will be the output of the following code: console.log(a); var a = 50;

What will happen if you declare a variable without 'var', 'let', or 'const'?

A). Creates a global variable

B). Creates a block-scoped variable

C). Creates a function-scoped variable

D). Throws an error

What will be the output of the following code: let y = 10; let y = 20; console.log(y);

A). 10

B). 20

C). Error

D). undefined

Which keyword allows block-scoped variable declaration?

A). var

B). let

C). const

D). Both B and C

What is the scope of a variable declared with 'let' inside a loop?

A). Global

B). Function

C). Loop block

D). Entire script

What is the default scope of variables declared with the 'var' keyword in JavaScript?

A). Block scope

B). Function scope

C). Module scope

D). Block and function scope

What will be the output of the following code: var x = 5; var x = 10; console.log(x);

A). 5

B). 10

C). Error

D). undefined

What will be the output of the following code: const d = 90; d = 100; console.log(d);

A). 90

B). 100

C). Error

D). undefined

Can 'const' be used to declare an array or object?

A). No, only primitives

B). Yes, but the reference can't change

C). Yes, and the content can't change

D). No

How does 'let' differ from 'var' in terms of scope?

A). No difference

B). Function-scoped

C). Block-scoped

D). Global-scoped

Which keyword is used for declaring variables that should not change?

A). var

B). let

C). const

D). all of the above