Can identifiers start with a digit in JavaScript?

Which of the following is a reserved word in JavaScript?

A). myVariable

B). function

C). let

D). number

What is a valid identifier in JavaScript?

A). 123abc

B). abc123

C). let

D). var

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

Which of the following is a valid identifier name?

A). var

B). 123abc

C). _123abc

D). #abc123

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

A). undefined

B). null

C). 5

D). x

Which identifier is valid in strict mode?

A). public

B). _public

C). 123public

D). public$

Which is a correct identifier for a variable?

A). 9variable

B). variable-9

C). variable_9

D). variable 9

Which characters are allowed in JavaScript identifiers?

A). Letters only

B). Letters and numbers only

C). Letters, numbers, $ and _

D). Any special characters

Which of the following is a valid identifier?

A). if

B). else

C). null

D). value1

Can an identifier be a single character?

A). Yes

B). No

C). Only in ES5

D). Only in ES6