Which of the following is an invalid identifier?

What is a valid identifier in JavaScript?

A). 123abc

B). abc123

C). let

D). var

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

Can JavaScript identifiers include spaces?

A). Yes

B). No

C). Only in ES6

D). Only in strings

Which identifier is valid in strict mode?

A). public

B). _public

C). 123public

D). public$

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

A). undefined

B). null

C). 5

D). x

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 the following is a valid identifier?

A). if

B). else

C). null

D). value1

Which of the following is a valid identifier name?

A). var

B). 123abc

C). _123abc

D). #abc123

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