Which of the following is a valid identifier name?

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

A). undefined

B). null

C). 5

D). x

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 a valid identifier?

A). if

B). else

C). null

D). value1

Which identifier is valid in strict mode?

A). public

B). _public

C). 123public

D). public$

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

What is the output of the following code: var x = 5, x = 10;

A). Syntax error

B). 5

C). 10

D). Reference error

Can JavaScript identifiers include spaces?

A). Yes

B). No

C). Only in ES6

D). Only in strings

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