Are JavaScript identifiers case-sensitive?

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

A). undefined

B). null

C). 5

D). x

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

A). Syntax error

B). Declares a variable

C). Throws a runtime error

D). Reassigns undefined

Which identifier is valid in strict mode?

A). public

B). _public

C). 123public

D). public$

Which is a correct identifier for a variable?

A). 9variable

B). variable-9

C). variable_9

D). variable 9

Can JavaScript identifiers include spaces?

A). Yes

B). No

C). Only in ES6

D). Only in strings

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

What is a valid identifier in JavaScript?

A). 123abc

B). abc123

C). let

D). var

What is the maximum length of an identifier?

A). 255 characters

B). 31 characters

C). 64 characters

D). No limit

Which of the following is an invalid identifier?

A). _variable

B). var$

C). 2variable

D). variable2

Which of the following is a valid identifier name?

A). var

B). 123abc

C). _123abc

D). #abc123