Grammar and types

Question 1

What are the three kinds of variable declarations

Answer 1

var - Declares a variable, optionally initializing it to a value

let - Declares a block-scoped, local variable, optionally initializing it to a value

const - Declares a block-scoped, read-only named constant

Question 2

What is a variable

Answer 2

Variables are symbolic names for values in your application

Question 3

What are the rules for variable names

Answer 3

A variable must start with a letter, underscore (_) or dollar ($) sign

Subsequent characters can also be digits (0-9)

It is case sensitive so letters include both upper (A-Z) and lower (a-z) cases

Question 4

What is variable scope

Answer 4

Variable scope can be either global or local

Global variable scope is when a variable is declared outside of any function and is available to any code within the current document

Local variable scope is when a variable is declared inside of a function and is only accessible within the function

Question 5

What is variable hoisting

Answer 5

Hoisting refers to the lifting of variables to the top of the function or statement calling them

Variables that are declared after they are called are returned as “undefined” rather than throwing an exception

Question 6

Describe function hoisting

Answer 6

A function declaration will run successfully without error as they are hoisted

A function expression on the other hand will return a TypeError indicating is not a function

Question 7

List the primitive (or simple) data types

Answer 7

1. Boolean - returns either true or false
2. null - a variable with no value
3. undefined - a variable that has been declared but no value assigned yet
4. Number - an integer or floating point number
5. String - a sequence of characters that represent a text value

Question 8

List the complex data type

Answer 8

Object - this includes arrays and functions as both are considered types of objects