Chapter 3: Variables

Question 1

JavaScript types can be divided into two categories: ______ types and ______ types

Answer 1

primitive, object

Question 2

The special JavaScript values null and undefined are _______ values, but they are not
numbers, strings, or booleans

Answer 2

primitive

Question 3

Any JavaScript value that is not a number, a string, a boolean, or null or undefined is
an _____

Answer 3

object

Question 4

JavaScript defines another special kind of object, known as a ______

Answer 4

function

Question 5

The most important thing about functions in JavaScript is that
they are true values and that JavaScript programs can treat them like _____

Answer 5

objects

Question 6

Functions that are written to be used (with the new operator) to initialize a newly created
object are known as ______

Answer 6

constructors

Question 7

Javascript types can be categorized as _____ and _____ types

Answer 7

mutable, immutable

Question 8

In javascript, strings are immutable

Answer 8

True

Question 9

JavaScript converts values liberally from one type to another. If a program expects a
string, for example, and you give it a number, it will automatically convert the number
to a string for you

Answer 9

True

Question 10

When a number appears directly in a JavaScript program, it’s called a _____ _______

Answer 10

numeric literal

Question 11

Javascript recognizes hexadecimal

Answer 11

True

Question 12

All numbers in JavaScript are represented as floating-point
values.

Answer 12

True

Question 13

JavaScript supports more complex
mathematical operations through a set of functions and constants defined as properties
of the ______ object:

Answer 13

Math

Question 14

There are infinitely many real numbers, but only a finite number of them
(18437736874454810627, to be exact) can be represented exactly by the JavaScript
floating-point format. This means that when you’re working with real numbers in
JavaScript, the representation of the number will often be an ______ of the
actual number.

Answer 14

approximation

Question 15

Core JavaScript includes a _____ constructor for creating objects that represent dates
and times.

Answer 15

Date()
var then = new Date(2010, 0, 1); // The 1st day of the 1st month of 2010
var later = new Date(2010, 0, 1, // Same day, at 5:10:30pm, local time
17, 10, 30);

Question 16

In javascript a string is _____

Answer 16

immutable

Question 17

To include a string literally in a JavaScript program, simply enclose the characters of
the string within a matched pair of ____ or _____

Answer 17

single, double quotes

Question 18

____ is an escape sequence that represents a newline character

Answer 18

\n

Question 19

One of the built-in features of JavaScript is the ability to _________ strings. If you use
the ____ operator with numbers, it adds them

Answer 19

concatenate, +

Question 20

In addition to this
______ property, there are a number of methods you can invoke on
strings

Answer 20

length
s.length

Question 21

Remember that strings are immutable in JavaScript. Methods like replace() and
toUpperCase() return new strings: they do not modify the string on which they are
invoked

Answer 21

TRUE

Question 22

____ and _____ for boolean values

Answer 22

true, false

Question 23

Boolean values have a _______ method that you can use to convert them to the strings
“true” or “false”

Answer 23

toString()

Question 24

______ is a language keyword that evaluates to a special value that is usually used to
indicate the absence of a value.

Answer 24

null

Question 25

The ______ object is a regular JavaScript object that serves a very important purpose: the properties of this object are the globally defined symbols that are available to a JavaScript program

Answer 25

global

Question 26

In top-level code—JavaScript code that is not part of a function—you can use the JavaScript keyword _____ to refer to the global object:

Answer 26

this

Question 27

When the value of a property is a function, we call it a _______. To invoke the method m of an object o, we write ____

Answer 27

method, o.m()

Question 28

Strings are not objects, though, so why do they have properties? Whenever you try to refer to a property of a string s, JavaScript converts the string value to an object as if by calling ____ ______. This object inherits (see §6.2.2) string methods and is used to resolve the property reference

Answer 28

new String(s)

Question 29

Numbers and booleans have methods for the same reason that strings do: a temporary object is created using the _____ or _______ constructor

Answer 29

Number), Boolean()

Question 30

The temporary objects created when you access a property of a string, number, or boolean are known as ______ ______

Answer 30

wrapper objects

Question 31

The _____ operator will also show you the difference between a primitive value and its wrapper object.

Answer 31

typeof

Question 32

Objects are not compared by value: two objects are not equal even if they have the same properties and values. And two arrays are not equal even if they have the same elements in the same order:

Answer 32

TRUEEEEE

Question 33

JavaScript is very flexible about the types of values it requires. We’ve seen this for booleans: when JavaScript expects a boolean value, you may supply a value of any type, and JavaScript will convert it as needed.

Answer 33

True

Question 34

Because JavaScript can convert values flexibly, its == _______ ______ is also flexible with its notion of equality

Answer 34

equality operators null == undefined // These two values are treated as equal. "0" == 0 // String converts to a number before comparing. 0 == false // Boolean converts to number before comparing. "0" == false // Both operands convert to numbers before comparing.

Question 35

The simplest way to perform an explicit type conversion is to use the ______, ______, ______, or ______ functions

Answer 35

Boolean(), Number(), String(), Object()

Question 36

______ parses only integers, while _______ parses both integers and floating-point numbers.

Answer 36

parseInt(), parseFloat()

Question 37

Both parseInt() and parseFloat() skip leading _______, parse as many numeric characters as they can, and ignore anything that follows. If the first nonspace character is not part of a valid numeric literal, they return _____:

Answer 37

NaN

Question 38

all objects (including arrays and functions) convert to ____. This is so even for wrapper objects: new Boolean(false) is an object rather than a primitive value, and so it converts to true.

Answer 38

true

Question 39

All objects inherit two conversion methods. The first is called ______, and its job is to return a string representation of the object.

Answer 39

toString()

Question 40

The other object conversion function is called ________

Answer 40

valueOf()

Question 41

Variables are declared with the ____ keyword

Answer 41

var var i; var sum;

Question 42

If you don’t specify an initial value for a variable with the var statement, the variable is declared, but its value is ________ until your code stores a value into it

Answer 42

undefined

Question 43

The ____ of a variable is the region of your program source code in which it is defined.

Answer 43

scope

Question 44

Function definitions can be nested

Answer 44

True

Question 45

This is called block scope, and JavaScript does not have it

Answer 45

True

Question 46

java script has ______ ______: variables are visible within the function in which they are defined and within any functions that are nested within that function. This means that even if a variabel is declared below but is used futrther up, if it is defined it is still valid because of _____ ____

Answer 46

function scope

Question 47

Since JavaScript does not have block scope, some programmers make a point of declaring all their variables at the ____ of the function

Answer 47

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