JavaScript

[Pages:630]JavaScript

#javascript

Table of Contents

About

1

Chapter 1: Getting started with JavaScript

2

Remarks

2

Versions

2

Examples

3

Using the DOM API

3

Using console.log()

4

Introduction

4

Getting Started

4

Logging variables

5

Placeholders

5

Logging Objects

6

Logging HTML elements

6

End Note

7

Using window.alert()

7

Notes

7

Using window.prompt()

8

Syntax

8

Examples

8

Notes

9

Using the DOM API (with graphical text: Canvas, SVG, or image file)

9

Using window.confirm()

10

Notes

11

Chapter 2: .postMessage() and MessageEvent

12

Syntax

12

Parameters

12

Examples

12

Getting Started

12

What is .postMessage(), when and why do we use it

12

Sending messages

12

Receiving, Validating and Processing Messages

13

Chapter 3: AJAX

15

Introduction

15

Remarks

15

Examples

15

Using GET and no parameters

15

Sending and Receiving JSON Data via POST

15

Displaying the top JavaScript questions of the month from Stack Overflow's API

16

Using GET with parameters

17

Check if a file exists via a HEAD request

17

Add an AJAX preloader

18

Listening to AJAX events at a global level

19

Chapter 4: Anti-patterns

20

Examples

20

Chaining assignments in var declarations.

20

Chapter 5: Arithmetic (Math)

21

Remarks

21

Examples

21

Addition (+)

21

Subtraction (-)

22

Multiplication (*)

22

Division (/)

22

Remainder / Modulus (%)

23

Using modulus to obtain the fractional part of a number

24

Incrementing (++)

24

Decrementing (--)

24

Common Uses

25

Exponentiation (Math.pow() or **)

25

Use Math.pow to find the nth root of a number.

26

Constants

26

Trigonometry

27

Sine

27

Cosine

28

Tangent

28

Rounding

28

Rounding

29

Rounding up

29

Rounding down

29

Truncating

29

Rounding to decimal places

30

Random Integers and Floats

31

Bitwise operators

31

Bitwise or

31

Bitwise and

32

Bitwise not

32

Bitwise xor (exclusive or)

32

Bitwise left shift

32

Bitwise right shift >> (Sign-propagating shift) >>> (Zero-fill right shift)

32

Bitwise assignment operators

33

Get Random Between Two Numbers

34

Random with gaussian distribution

34

Ceiling and Floor

35

Math.atan2 to find direction

36

Direction of a vector

36

Direction of a line

36

Direction from a point to another point

36

Sin & Cos to create a vector given direction & distance

36

Math.hypot

37

Periodic functions using Math.sin

37

Simulating events with different probabilities

39

Little / Big endian for typed arrays when using bitwise operators

40

Getting maximum and minimum

41

Getting maximum and minimum from an array:

41

Restrict Number to Min/Max Range

42

Getting roots of a number

42

Square Root

42

Cube Root

42

Finding nth-roots

42

Chapter 6: Arrays

43

Syntax

43

Remarks

43

Examples

43

Standard array initialization

43

Array spread / rest

44

Spread operator

44

Rest operator

45

Mapping values

45

Filtering values

46

Filter falsy values

47

Another simple example

47

Iteration

47

A traditional for-loop

48

Using a traditional for loop to loop through an array

48

A while loop

49

for...in

49

for...of

49

Array.prototype.keys()

50

Array.prototype.forEach()

50

Array.prototype.every

51

Array.prototype.some

51

Libraries

52

Filtering Object Arrays

52

Joining array elements in a string

54

Converting Array-like Objects to Arrays

54

What are Array-like Objects?

54

Convert Array-like Objects to Arrays in ES6

55

Convert Array-like Objects to Arrays in ES5

55

Modifying Items During Conversion

56

Reducing values

57

Array Sum

57

Flatten Array of Objects

57

Map Using Reduce

58

Find Min or Max Value

58

Find Unique Values

59

Logical connective of values

59

Concatenating Arrays

60

Append / Prepend items to Array

62

Unshift

62

Push

62

Object keys and values to array

62

Sorting multidimensional array

63

Removing items from an array

63

Shift

63

Pop

64

Splice

64

Delete

65

Array.prototype.length

65

Reversing arrays

65

Remove value from array

66

Checking if an object is an Array

66

Sorting Arrays

67

Shallow cloning an array

69

Searching an Array

70

FindIndex

70

Removing/Adding elements using splice()

70

Array comparison

71

Destructuring an array

72

Removing duplicate elements

72

Removing all elements

73

Method 1

73

Method 2

74

Method 3

74

Using map to reformat objects in an array

74

Merge two array as key value pair

75

Convert a String to an Array

76

Test all array items for equality

76

Copy part of an Array

77

begin

77

end

77

Example 1

77

Example 2

77

Finding the minimum or maximum element

78

Flattening Arrays

79

2 Dimensional arrays

79

Higher Dimension Arrays

79

Insert an item into an array at a specific index

80

The entries() method

80

Chapter 7: Arrow Functions

82

Introduction

82

Syntax

82

Remarks

82

Examples

82

Introduction

82

Lexical Scoping & Binding (Value of "this")

83

Arguments Object

84

Implicit Return

84

Explicit Return

85

Arrow functions as a constructor

85

Chapter 8: Async functions (async/await)

86

Introduction

86

Syntax

86

Remarks

86

Examples

86

Introduction

86

Arrow function style

87

Less indentation

87

Await and operator precedence

87

Async functions compared to Promises

88

Looping with async await

90

Simultaneous async (parallel) operations

91

Chapter 9: Async Iterators

93

Introduction

93

Syntax

93

Remarks

93

Useful Links

93

Examples

93

Basics

93

Chapter 10: Automatic Semicolon Insertion - ASI

95

Examples

95

Rules of Automatic Semicolon Insertion

95

Statements affected by automatic semicolon insertion

95

Avoid semicolon insertion on return statements

96

Chapter 11: Battery Status API

98

Remarks

98

Examples

98

Getting current battery level

98

Is battery charging?

98

Get time left until battery is empty

98

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