Which of the following is an invalid identifier?

Can identifiers start with a digit in JavaScript?

A). Yes

B). No

C). Only in ES5

D). Only in strict mode

What is the maximum length of an identifier?

A). 255 characters

B). 31 characters

C). 64 characters

D). No limit

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

Which of these is an invalid identifier?

A). foo_bar

B). fooBar

C). foo-bar

D). foo$bar

Can an identifier be a single character?

A). Yes

B). No

C). Only in ES5

D). Only in ES6

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

Can JavaScript identifiers include spaces?

A). Yes

B). No

C). Only in ES6

D). Only in strings

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 name?

A). var

B). 123abc

C). _123abc

D). #abc123