Can JavaScript identifiers include spaces?

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

A). undefined

B). null

C). 5

D). x

Which of the following is a valid identifier?

A). if

B). else

C). null

D). value1

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 a valid identifier name?

A). var

B). 123abc

C). _123abc

D). #abc123

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

A). No error

B). Syntax error

C). Logical error

D). Runtime error

Are JavaScript identifiers case-sensitive?

A). Yes

B). No

C). Only in ES6

D). Only in strict mode

Which of the following is an invalid identifier?

A). _variable

B). var$

C). 2variable

D). variable2

What is the maximum length of an identifier?

A). 255 characters

B). 31 characters

C). 64 characters

D). No limit

Can an identifier be a single character?

A). Yes

B). No

C). Only in ES5

D). Only in ES6