Can JavaScript identifiers include spaces?

Which of the following is a valid identifier name?

A). var

B). 123abc

C). _123abc

D). #abc123

Which of these is an invalid identifier?

A). foo_bar

B). fooBar

C). foo-bar

D). foo$bar

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

A). undefined

B). null

C). 5

D). x

Can an identifier be a single character?

A). Yes

B). No

C). Only in ES5

D). Only in ES6

Which characters are allowed in JavaScript identifiers?

A). Letters only

B). Letters and numbers only

C). Letters, numbers, $ and _

D). Any special characters

Which identifier is valid in strict mode?

A). public

B). _public

C). 123public

D). public$

Which of the following is a valid identifier?

A). if

B). else

C). null

D). value1

Which of the following is an invalid identifier?

A). _variable

B). var$

C). 2variable

D). variable2

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

What is the maximum length of an identifier?

A). 255 characters

B). 31 characters

C). 64 characters

D). No limit