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JavaScript > Intermediate JavaScript > Flashcards

Intermediate JavaScript Flashcards

1
Q

What is the DOM

A

Document Object Model

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2
Q

What is the Virtual DOM?

A

A virtual DOM is a lightweight JavaScript representation of the DOM used in declarative web frameworks such as React, Vue.js, and Elm. Updating the virtual DOM is comparatively faster than updating the actual DOM.

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3
Q

Window Object

A

Represents the browser window

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4
Q

Document Object

A

Represents the web page

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5
Q

Image Object

A

Represents an HTML IMG tag

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6
Q

History Object

A

Contains browser history

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7
Q

Navigator Object

A

Contains niformation about the visitor’s browser

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8
Q

All global JS objects, functions and variables automatically become….

A

members of the window object

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9
Q

Global variables (Window object) are…

A

properties of the window object

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10
Q

Global functions (window object) are..

A

methods of the window object

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11
Q

Some methods of the Window Object

A

window. open
window. close
window. moveTo
window. resizeTo

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12
Q

Finding HTML (Document Object), few examples

A

getElementsById
getElementsByTagName
getElementsByClassName

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13
Q

Changing HTML (Document Object)

A

element. innerHTML =
element. attribute =
element. setAttribute (attribute,value)

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14
Q

Adding or Deleting Elements (Document Object)

A

document. createElement(element)
document. removeChild(element)
document. appendChild(element)

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15
Q

Event Handler (Document Object)

A

document.getElementById(id).onclick = function () {code}

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16
Q

Create an Image Object

A

const x = document.createElement(“IMG”)

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17
Q

Some Image Object properties

A

complete
naturalHeigth
naturalWidth
src

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18
Q

Image rollover?

A

Two images. Change onMouseOver and onMouseOut

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19
Q

Return the anchor part of a URL (Location Object)

A

var x = location.hash;

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20
Q

Which Methods are there for the Location Object?

A

assign() Loads a new document
reload() Reloads the current document
replace() Replaces the current document with a new one

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21
Q

Difference between replace or assign (location object)

A

After using replace the current page will not be saved in the session history

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22
Q

Which Navigator propertie returns the version of the browser?

A

appVersion

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23
Q

Which Navigator object returns the operating system?

A

platform

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24
Q

Which Navigator property returns the name of the browser?

A

appName

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25
Q

Which three methods to extract a part of String are there?

A

slice(start, end)
substring(start, end)
substr(start, length)

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26
Q

What does slice()? (String)

A

extracts a part of a string and returns the extracted part in a new string.

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27
Q

What doest the substring() method?

A

substring() is similar to slice().

The difference is that substring() cannot accept negative indexes.

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28
Q

What does the substr() method?

A

substr() is similar to slice().

The difference is that the second parameter specifies the length of the extracted part.

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29
Q

Difference between indexOf() and search() method?

A 
The search() method cannot take a second start position argument.
The indexOf() method cannot take powerful search values (regular expressions).
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30
Q

String.match….

A

The match() method searches a string for a match against a regular expression, and returns the matches, as an Array object.

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31
Q

What is a regular expression? Regexp

A

A regular expression is a sequence of characters that forms a search pattern.
The search pattern can be used for text search and text replace operations.

32
Q

In JavaScript, regular expressions are often used with the two string methods: search() and replace().

A

The search() method uses an expression to search for a match, and returns the position of the match.

The replace() method returns a modified string where the pattern is replaced.

33
Q

Regular Expression Patterns

A

Brackets are used to find a range of characters:

Expression
[abc] Find any of the characters between the brackets
[0-9] Find any of the digits between the brackets
(x|y) Find any of the alternatives separated with |
Metacharacters are characters with a special meaning:

Metacharacter
\d Find a digit
\s Find a whitespace character
\b Find a match at the beginning of a word like this: \bWORD, or at the end of a word like this: WORD\b
\uxxxx Find the Unicode character specified by the hexadecimal number xxxx

34
Q

RegExp Object

A

In JavaScript, the RegExp object is a regular expression object with predefined properties and methods.

35
Q

Reg Exp Object methods

A

exec() Tests for a match in a string. Returns the first match
test() Tests for a match in a string. Returns true or false
toString() Returns the string value of the regular expression

36
Q

What type of error is most likely to debug using watchpoints?

A

Logical

37
Q

What is a typical watchpoint in JS?

A

alert()

38
Q

What type of error after script has loaded?

A

Run-time

39
Q

What are run time erros typically caused by?

A

Improper use of commands

40
Q

Syntax-error

A

Load time (also called compiler / interpreter error)

41
Q

What to use to repeat a group of statement fora particular range of values?

A

For loop

42
Q

Control structures…

A

Make decisions based on Boolean values

43
Q

Substitute for the neste if..else statement?

A

Switch

44
Q

Purpose of the switch statement?

A

To compare a value against another to search for a match

45
Q

Purpose of the break statement?

A

To exit a control structure

46
Q

Continue statement..

A

Force the flow of control back to the top of the loop

47
Q

How to check if Java is enabled?

A

Use javaEnabled() method (navigator object)

48
Q

Limitation of virtual DOM?

A

Changes aren’t directly reflected on the webpage

49
Q

The history object has one property….

A

length

50
Q

What is the JS equivalent fo the browser’s back button?

A

history.go(-1);

51
Q

What is the default object in JS?

A

Window

52
Q

How to bring a window object to the top?

A

window.moveTo()

53
Q

Create a new history entry?

A

pushstate()

54
Q

Diffing =

A

comparing the new virtual DOM with previous version

55
Q

window.open() method uses 3 segments

A

URL, window name and list of window

56
Q

Comma delimited list from array

A

Use myArray.join(“,”);

57
Q

Declare a regular expression:

A

var ex = /Ron/;

58
Q

Difference between shift and pop

A

shift removes and returns the first element, pop the last element

59
Q

How to extract username from var email = ron@outlook.com

A

email.substring(0, email.indexOf(“@”)
0 = starting index
@ = starting index –> up to (in this case @ )

60
Q

To use any Data or Time you must create a new instance or copy

A

var mydate = new Date();

61
Q

How to repeat a method or command after x-time

A

setTimeOut()

function.setTimeOut(time);

62
Q

The join() method, by default, uses the….

A

comma seperator

63
Q

Why use regular expression instead of string for matching?

A

regular expression can match a large number of strings

64
Q

Math.random returns…

A

any value in range 0 - 1 with 0 included and 1 excluded

65
Q

getDate() returns…

A

The date number (17 if it’s 17th of november)

66
Q

Regex, string, Math, Array, Date are….

A

language objects

67
Q

String length is…

A

string.length (NOT a method so no brackets)

68
Q

floor, ceil, sin are…

A

Math objects

69
Q

substr() method takes two parameters…

A
  1. Starting index

2. Number of characters to extract

70
Q

charAt() example..

A

firstName.charAt(4);

71
Q

What is a JS class?

A 
A JavaScript class is not an object.
It is a template for JavaScript objects.
72
Q

THe prototype is available in …… JS object

A

every

73
Q

Inheritance =

A

class-based and prototype based

74
Q

Yield operator

A

Pause or resume a generator function

75
Q

Add additional fields to custom object…

A

Use prototype

76
Q

Which object can access items in a collection?

A

Iterator

77
Q

Call the functions on a paretn object?

A

Use the super keyword

JavaScript (6 decks)

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