language syntax

Question 1

javascript types

Answer 1

Primitives:
- number
- string
- boolean
- null
- undefined
Objects:
- global object
- object
- array
- function (including constructors)
- date
- regexp
- error

Question 2

javascript type categories

Answer 2

• primitive vs. object
• with methods vs. without methods
• mutable vs. inmutable

Question 3

var

Answer 3

variable declaration

Question 4

overflow

Answer 4

the result of a numeric operation is larger than the largest representable number, negative or positive, resulting in the return of Infinity or -Infinity

Question 5

underflow

Answer 5

occurs when the result of a numeric operation is closer to zero than the smallest representable number, resulting in a return of zero or negative zero

Question 6

monetary values

Answer 6

manipulate monetary values as integer cents rather than fractional dollars

Question 7

\n

Answer 7

escape sequence for newline

Question 8

'

Answer 8

escape sequence for single quote

Question 9

\u

Answer 9

escape sequence for unicode characters

Question 10

+

Answer 10

string concatenation overloaded operator

Question 11

string.length

Answer 11

returns the length of a string in 16bit values (note, some characters are more than 16bits)

Question 12

string.charAt(x)

Answer 12

returns the character at the index given

Question 13

string.substring(x,y)

Answer 13

returns characters between x and y

Question 14

string.slice(x) or string.slice(x,y)

Answer 14

returns the characters between x and y, or x number of characters

Question 15

string.indexOf(x)

Answer 15

returns index of given character

Question 16

string.lastIndexOf(x)

Answer 16

returns index of last occurrence of given character

Question 17

string.split(“x”)

Answer 17

split string into substrings

Question 18

string.replace(x, y)

Answer 18

replace x for y on all instances

Question 19

string.toUpperCase()

Answer 19

all characters in string to uppercase

Question 20

immutable strings

Answer 20

in js strings are immutable. Methods like .replace() and .toUpperCase() return new strings

Question 21

string[x]

Answer 21

return character at position x

Question 22

/^HTML/

Answer 22

regular expression example - expression is indicated between two forward slashes

Question 23

RegExp()

Answer 23

constructor for regular expressions

Question 24

string.test(text)

Answer 24

string method for finding text pattern - returns true if matched

Question 25

string.search(pattern)

Answer 25

returns index position of first match

Question 26

string.match(pattern)

Answer 26

returns array of all matches

Question 27

true

Answer 27

truthy boolean value

Question 28

false

Answer 28

falsy boolean value

Question 29

falsy values

Answer 29

- false - undefined - null - 0 - -0 - NaN - "" (empty string)

Question 30

if (x !== null)

Answer 30

Execute statement if x is not null (if it holds a value or an object)

Question 31

if (x)

Answer 31

Execute statement if x is not false (if it holds a truthy value)

Question 32

boolean.toString()

Answer 32

Convert boolean to string "true" or "false"

Question 33

&&

Answer 33

boolean AND operator

Question 34

||

Answer 34

boolean OR operator

Question 35

!

Answer 35

boolean NOT operator

Question 36

null

Answer 36

indicates absence of a value

Question 37

undefined

Answer 37

indicates the value of a variable that has not been initialized, value of an object property that does not exist, or array element that does not exist. also returned by functions that have no return value, and value of function parameters for which no value has been supplied

Question 38

undefined vs. null

Answer 38

undefined - represent a system-level, unexpected, or error-like absence of value null - represent program-level, normal, or expected absence of value NOTE: If you need to assign one of these values to a variable or property or pass one of these values to a function, null is almost always the right choice

Question 39

global object

Answer 39

the properties of this object are the globally defined symbols that are available to a JavaScript program

Question 40

global object properties

Answer 40

* global properties like undefined, Infinity, and NaN * global functions like isNaN(), parseInt() , and eval() * constructor functions like Date(), RegExp(), String(), Object(), and Array() * global objects like Math and JSON

Question 41

Global

Answer 41

name of global object

Question 42

Window

Answer 42

client side (browser) global object

Question 43

var global = this;

Answer 43

Define a global variable to refer to the global object

Question 44

this

Answer 44

when used in top level code (outside a function), it refers to the global object

Question 45

window

Answer 45

the global Window object has a | self-referential 'window' property that can be used instead of this to refer to the global object

Question 46

object.method()

Answer 46

a property that has a function as a value

Question 47

String(), Number(), Boolean()

Answer 47

wrapper objects - constructors that create temporary objects. these objects are used to provide properties to primitive data types. these properties are read only

Question 48

immutable values

Answer 48

strings, numbers, booleans

Question 49

object values

Answer 49

objects are 'reference types', and they are compared by reference. two object values are the same if they refer to the same underlying object

Question 50

copying an array

Answer 50

``` var a = ['a','b','c']; var b = []; for(var i = 0; i < a.length; i++) { b[i] = a[i]; } ```

Question 51

comparing two arrays

Answer 51

``` function equalArrays(a,b) { if (a.length != b.length) return false; for(var i = 0; i < a.length; i++) { if (a[i] !== b[i]) return false; } return true; } ```

Question 52

type conversion

Answer 52

if JavaScript wants a string, it will convert whatever value you give it to a string. If JavaScript wants a number, it will try to convert the value you give it to a number. js will return NaN if it cannot perform a meaningful conversion

Question 53

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

Answer 53

explicit conversion of one data type into another. | NOTE: use these without the new operator, otherwise you will end up with a wrapper object

Question 54

toString()

Answer 54

convert value to a string | NOTE: not supported for null or undefined

Question 55

x + ""

Answer 55

same as String(x)

Question 56

+x

Answer 56

same as Number(x)

Question 57

!!x

Answer 57

same as Boolean(x)

Question 58

binary_string = n.toString(2);

Answer 58

convert to binary string. Evaluates to "10001"

Question 59

octal_string = "0" + n.toString(8);

Answer 59

convert to octal string. Evaluates to "021"

Question 60

toFixed()

Answer 60

converts a number to a string with a specified number | of digits after the decimal point

Question 61

toExponential()

Answer 61

converts a number to a string using exponential notation, with one digit before the decimal point and a specified number of digits after the decimal point

Question 62

toPrecision()

Answer 62

converts a number to a string with the number of significant digits you specify

Question 63

Number()

Answer 63

attempts to parse that string as an integer or floating-point literal

Question 64

parseInt()

Answer 64

parses only integers

Question 65

parseFloat()

Answer 65

parses both integers and floating-point numbers

Question 66

valueOf()

Answer 66

it is supposed to convert an object to a primitive value that represents the object, if any such primitive value exists

Question 67

var x;

Answer 67

variable declaration. always use var to declare variables, otherwise the variables will be assigned as properties of the global object

Question 68

var greeting = "hello";

Answer 68

variable initialization

Question 69

'scope' of a variable

Answer 69

the region of your program source code in which it is defined

Question 70

'global' variable

Answer 70

has global scope; it is defined everywhere in your JavaScript code

Question 71

'local' variables

Answer 71

variables declared within a function are defined only within the bodyof the function. They have local scope