JavaScript module 2

Question 1

What is a method?

Answer 1

a property of an object that contains a function definition

Question 2

How can you tell the difference between a method definition and a method call?

Answer 2

one is defined with a body and if it doesn’t have the body its a call

Question 3

Describe method definition syntax (structure).

Answer 3

lick: function () {
return ‘mlem’;
}

Question 4

Describe method call syntax (structure).

Answer 4

object.method()

Question 5

How is a method different from any other function?

Answer 5

its pre defined

Question 6

What is the defining characteristic of Object-Oriented Programming?

Answer 6

object’s own procedures can access and often modify the data fields of itself

Question 7

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

Answer 7

Abstraction
Encapsulation
Inheritance
Polymorphism

Question 8

What is “abstraction”?

Answer 8

a way of representing a complex process with a series of steps

Question 9

What does API stand for?

Answer 9

Application programming interface

Question 10

What is the purpose of an API?

Answer 10

a way for programs to communicate with each other

Question 11

What is this in JavaScript?

Answer 11

a JavaScript keywords that references the current object. It has different values depending on where it is used: In a method, this refers to the owner object. Alone, this refers to the global object. In a function, this refers to the global object.

Question 12

When is the value of this determined in a function; call time or definition time?

Answer 12

call time

Question 13

1.What does this refer to in the following code snippet
var character = {
  firstName: 'Mario',
  greet: function () {
    var message = 'It\'s-a-me, ' + this.firstName + '!';
    console.log(message);
  }
};

2. Given the above character object, what is the result of the following code snippet? Why?
   character. greet();

3.Given the above character object, what is the result of the following code snippet? Why?
var hello = character.greet;
hello();

Answer 13

1. the character object.
2. its a me mario!
3. it’s a me undefined!, because its a stand alone function so “this” would be refering to the window

Question 14

How can you tell what the value of this will be for a particular function or method definition?

Answer 14

you can guess if its used as you intended for it to be used

Question 15

How can you tell what the value of this is for a particular function or method call?

Answer 15

for a function its a window

for a method if its a property of an object than its the object if its a nothing then its the window

Question 16

What kind of inheritance does the JavaScript programming language use?

Answer 16

prototype based inheritance

Question 16

What kind of inheritance does the JavaScript programming language use?

Answer 16

prototype-based (or prototypal) inheritance.

Question 17

What is a prototype in JavaScript?

Answer 17

where JavaScript looks for a property if the object itself doesn’t have it

Question 18

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

Answer 18

they are all represented by objects

Question 19

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

Answer 19

it looks at the prototype of the current object

Question 20

What does the new operator do?

Answer 20

lets developers create an instance of a user-defined object type or of one of the built-in object types that has a constructor function

Question 21

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

Answer 21

prototype property

Question 22

What does the instanceof operator do?

Answer 22

used to test if an object is of a given type(a descendant of). The result of the operation is either true or false

Question 23

What does it mean to say that this is an “implicit parameter”?

Answer 23

that it changes meaning depending where its called

Question 24

what is a callback function

Answer 24

a function that is passed in another function as an argument

Question 25

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 25

using the setTimeout() method

Question 26

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

Answer 26

setInterval() method

Question 27

What is the default time delay if you omit the delay parameter from setTimeout() or setInterval() and deos that mean it executes immediately?

Answer 27

0 and no set timeout will be the last thing to run if you have other code, for example a function that has to run 1000x, that will run first and then after its done the setTimeout() method will run. it pretty much deprioroitizes whatever is in setTimeout() at 0

Question 28

What do setTimeout() and setInterval() return?

Answer 28

it returns an interval ID | of the data type number