Can identifiers start with a digit in JavaScript?

What is a valid identifier in JavaScript?

A). 123abc

B). abc123

C). let

D). var

Is let a valid identifier in JavaScript?

A). Yes

B). No

C). Only in ES6

D). Only in non-strict mode

Which of the following is a reserved word in JavaScript?

A). myVariable

B). function

C). let

D). number

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

Can JavaScript identifiers include spaces?

A). Yes

B). No

C). Only in ES6

D). Only in strings

What is the output of the following code: var x = 5, x = 10;

A). Syntax error

B). 5

C). 10

D). Reference error

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

Can an identifier be a single character?

A). Yes

B). No

C). Only in ES5

D). Only in ES6

Which is a correct identifier for a variable?

A). 9variable

B). variable-9

C). variable_9

D). variable 9