Quiz: Quiz 2: Variables and Data Types | Module 2: Variables, Data Types, Type Casting, and Comments

1. Which keyword is used to declare a variable in modern JavaScript that can be reassigned?

var

let

const

static

2. What is the data type of the value `true` in JavaScript?

String

Number

Boolean

Null

3. Which of the following is a valid JavaScript variable name?

2myVar

my-Var

$myVar

let

4. What is the result of `Number("10.5")`?

10

10.5

NaN

"10.5"

5. How do you write a single-line comment in JavaScript?

/* This is a comment */

// This is a comment

# This is a comment

6. What will `typeof null` return in JavaScript?

"null"

"undefined"

"object"

"boolean"

7. Which of these is an example of a complex data type in JavaScript?

String

Number

Array

Boolean

8. If `let x = 10;` and then `const x = 20;` is written in the same scope, what happens?

x becomes 20.

A TypeError occurs.

A SyntaxError occurs.

x remains 10.

9. What is the value of `myVar` after this code: `let myVar;`?

null

0

"" (empty string)

undefined