What will happen if you declare a variable with the name undefined?

Can an identifier be a single character?

A). Yes

B). No

C). Only in ES5

D). Only in ES6

What will the following code output: var x; x = 5; var y = x;

A). undefined

B). null

C). 5

D). x

Are JavaScript identifiers case-sensitive?

A). Yes

B). No

C). Only in ES6

D). Only in strict mode

Can identifiers start with a digit in JavaScript?

A). Yes

B). No

C). Only in ES5

D). Only in strict mode

Which of the following is an invalid identifier?

A). _variable

B). var$

C). 2variable

D). variable2

What is a valid identifier in JavaScript?

A). 123abc

B). abc123

C). let

D). var

What does the following code do: var $ = 5;

A). Throws an error

B). Creates a variable named $

C). Creates a variable named var

D). None of the above

Which of these is an invalid identifier?

A). foo_bar

B). fooBar

C). foo-bar

D). foo$bar

What will be the result of using a reserved word as an identifier?

A). No error

B). Syntax error

C). Logical error

D). Runtime error

Is let a valid identifier in JavaScript?

A). Yes

B). No

C). Only in ES6

D). Only in non-strict mode