JavaScript 2

Question 1

• What is JSON?

Answer 1

• JavaScript Object Notation, A text-based data format following JavaScript object syntax, it exists as a string

Question 2

• What are serialization and deserialization?

Answer 2

• Converting a native object to a string is serialization while converting a a string to a native object is called deserialization

Question 3

• Why are serialization and deserialization useful?

Answer 3

• To transmit data across a network and to receive it from the network.
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Question 4

How do you serialize a data structure into a JSON string using JavaScript?

Answer 4

• JSON.stringify();

Question 5

• How do you deserialize a JSON string into a data structure using JavaScript?

Answer 5

• JSON.parse();

Question 6

• How to you store data inlocalStorage?

Answer 6

• localStorage.setItem();

Question 7

• How to you retrieve data fromlocalStorage?

Answer 7

• localStorage.getItem();

Question 8

• What data type canlocalStoragesave in the browser?

Answer 8

• Strings

Question 9

• When does the’beforeunload’event fire on thewindowobject?

Answer 9

• It fires a window before everything is unloaded to cancel the event before the browser unloads all the information stored.

Question 10

• What DOM element property tells you what type of element it is?

Answer 10

• . .tagName;

Question 11

• Describe methoddefinitionsyntax (structure).

Answer 11

• Stored in an object a property and anonymous function definition

Question 12

• Describe methodcallsyntax (structure)

Answer 12

• .method();

Question 13

• What is thedefining characteristicof Object-Oriented Programming?
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Answer 13

• objects can contain both data (as properties) and behavior (as methods).

Question 14

• What are the four “principles” of Object-Oriented Programming?

Answer 14

• Abstraction, inheritance, encapsulation and polymorphism

Question 15

• What is “abstraction”?

Answer 15

• Being able to work with complex things in simple ways. Like a light switch or automatic transmission.

Question 16

• What does API stand for?

Answer 16

• Application programming Interface.

Question 17

• What is the purpose of an API?

Answer 17

• To give programmers a way to interact with a system in a simplified consistent fashio

Question 18

• What isthisin JavaScript?

Answer 18

• This implicit parameter of every javascript function that contains
  a reference to the object is bring called from

Question 19

• What does it mean to say thatthisis an “implicit parameter”?

Answer 19

• Its always available we don’t need to write it

Question 20

• Whenis the value ofthisdetermined in a function;call timeordefinition time?

Answer 20

• Call

Question 21

• How can you tell what the value ofthiswill be for a particular function or methoddefinition?

Answer 21

• It won’t be anything

Question 22

• How can you tell what the value ofthisis for a particular function or methodcall?
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Answer 22

• its the object next to the method

Question 23

• What kind of inheritance does the JavaScript programming language use?

Answer 23

• Prototypal inheritance

Question 24

• What is a prototype in JavaScript?

Answer 24

a JavaScript prototype is simply an object that contains properties and (predominantly) methods that can be used by other objects.

Question 25

* How is it possible to call methods on strings, arrays, and numbers even though those methods don't actually exist on strings, arrays, and numbers?

Answer 25

* They inherit them from the prototype object

Question 26

* If an object does not have it's own property or method by a given key, where does JavaScript look for it?

Answer 26

* Prototype

Question 27

* What does the new operator do?

Answer 27

* Creates a blank plain object and adds a property to the new object _proto_ , it binds the new created object as the this context and return this if the function doesn’t return an object

Question 28

* What property of JavaScript functions can store shared behavior for instances created with new?

Answer 28

* Proto

Question 29

* What does the instanceof operator do?

Answer 29

* Tests to see if the prototype property of a constructor appears in the prototype chain of an object, it returns a boolean

Question 30

* What is a "callback" function?

Answer 30

* A function definition stored as an argument

Question 31

* Besides adding an event listener callback function to an element or the document, what is one way to delay the execution of a JavaScript function until some point in the future?

Answer 31

* setTimeout()

Question 32

* How can you set up a function to be called repeatedly without using a loop?

Answer 32

* setInterval()

Question 33

* What is the default time delay if you omit the delay parameter from setTimeout() or setInterval()?

Answer 33

* 0

Question 34

* What do setTimeout() and setInterval() return?

Answer 34

* A positive integer value to identify the timer