Which identifier is valid in strict mode?

Which of the following is an invalid identifier?

A). _variable

B). var$

C). 2variable

D). variable2

Which characters are allowed in JavaScript identifiers?

A). Letters only

B). Letters and numbers only

C). Letters, numbers, $ and _

D). Any special characters

Are JavaScript identifiers case-sensitive?

A). Yes

B). No

C). Only in ES6

D). Only in strict mode

Which of these is an invalid identifier?

A). foo_bar

B). fooBar

C). foo-bar

D). foo$bar

Which of the following is a reserved word in JavaScript?

A). myVariable

B). function

C). let

D). number

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

A). undefined

B). null

C). 5

D). x

Is let a valid identifier in JavaScript?

A). Yes

B). No

C). Only in ES6

D). Only in non-strict mode

What is the maximum length of an identifier?

A). 255 characters

B). 31 characters

C). 64 characters

D). No limit

Can an identifier be a single character?

A). Yes

B). No

C). Only in ES5

D). Only in ES6

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