Can identifiers start with a digit in JavaScript?

Which of the following is an invalid identifier?

A). _variable

B). var$

C). 2variable

D). variable2

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

A). undefined

B). null

C). 5

D). x

Can JavaScript identifiers include spaces?

A). Yes

B). No

C). Only in ES6

D). Only in strings

Which is a correct identifier for a variable?

A). 9variable

B). variable-9

C). variable_9

D). variable 9

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

Which of the following is a reserved word in JavaScript?

A). myVariable

B). function

C). let

D). number

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

Are JavaScript identifiers case-sensitive?

A). Yes

B). No

C). Only in ES6

D). Only in strict mode